high resolution orthorectified imagery lidar data

High Resolution Orthorectified Imagery LiDAR Data Acquisition, Digital Elevation Model,

1-foot contours and Structures data within Floodplains

GIS Department 928-777-1309

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GENERAL INFORMATION Introduction The City of Prescott is seeking a qualified contractor to produce digital, low-level high-resolution orthophotographs and generate a new digital elevation model and one-foot interval contours of its City and surrounding area, for the use within the City of Prescott GIS system, and for engineering design, survey, infrastructure, transportation, planning, drainage, and other City projects. For the purposes of this project, a digital orthophotograph is defined as a geo-referenced image prepared from perspective photography, or other remotely-sensed data in which the displacement within the image due to sensor orientation and terrain relief has been removed. A digital orthophotograph represents the combination of photographic image characteristics with the geometric qualities of a map. Some examples of what the product of this project should allow users to identify are: hydrants, manholes, road striping and utility poles. It is intended that the products of the RFP will allow the municipality to provide better and more accurate digital representation of what is actually on the ground. The municipality may use this imagery to refine and improve upon the digital overlay data, develop more accurate storm water infrastructure delineations, map water and sewer system lines and connections, and inform land use planning projects. Three-dimensional modeling is becoming more important to municipal utility management. Digital Terrain Models (DTMs) developed for photogrammetric corrections in the development of the orthoimagery will also be used for a variety of other purposes. For this reason, the City of Prescott seeks to develop the most detailed DTM possible with the limited budget available for this project. City of Prescott Aerial Imagery Background The City last acquired imagery in early 2016- the aerial imagery captured produced 4-inch resolution imagery. Prior to that, imagery from 2012 (6-inch resolution in city, 1 ft outside city and LiDAR flight), 2008, 2004, 2002, 2000 and 1998 was acquired, and is archived on the GIS. The municipal staff uses ArcMap 10.7 as a GIS editing environment with data stored in SQL Server using ArcGIS Server for a variety of purposes. Departments using GIS include Engineering, Water, Wastewater, Planning and Zoning, Police, Fire, Dispatch, Golf Course, Parks and Recreation, Legal, Administrative Services, Finance, City Clerk, Airport, and Economic Development. The high-resolution orthoimagery will benefit numerous staff in our ability to provide responsive service to residents.

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SCOPE OF WORK The following scope of work has been developed by the City of Prescott staff. The imagery area covers approximately 105 square miles for the primary area and 7 square miles for an optional added area. A map of the proposed areas is included as part of Exhibit A. A. Image Acquisition The contractor shall acquire imagery to support high resolution digital orthophotographs. Acquisition Timing and Conditions Photo acquisition for this project in the spring of 2020 (once snow melt has occurred), pursuant to agreement between the City and the contractor. Images will be captured in leaf-off conditions of vegetation with minimal shadowing from sun angle, when the area is free of clouds, haze, fog, dust, smoke, floodwaters, and the ground is free of snow (particularly important for the south side of town). Photo acquisition shall not begin without authorization from the City of Prescott Project Manager. Photographic Mission The contractor shall be responsible for applying for, and obtaining, any required permit for access, overflight, or intrusion into restricted or otherwise limited ground access and/or airspace, which may be included within the requirement of this scope of services. Every effort shall be made to avoid breaks within individual flight lines. Where breaks within a flight line are necessary, the entire flight line composed of the resulting segments shall meet all of the requirements set forth in these Specifications. Where breaks occur, these shall have an overlap of at least four frames to ensure a stereo model of overlap or tie. All photos within a single flight line shall be acquired with the same aerial camera and with the camera oriented in the same direction. Overlap/Sidelap All photography shall be acquired to provide adequate stereo coverage. Minimum overlap shall be 60% forward and 30% side. However, additional exposures shall be captured over urban core areas and mountain areas to ensure that no more than 25% of roadways/transportation features are obscured in urban areas and valley bottoms are visible in the mountains. The imagery should not contain any objectionable shadows caused by terrain relief or low solar altitude. Image Quality All images should be clear and sharp in detail with no light streaks, static marks, scratches, dust marks, or other noticeable blemishes. The imagery should be free from defects, such as out-of-focus imagery, and should not contain inconsistencies in tone and/or density between individual orthos and/or adjacent sheets. To ensure consistency, the imagery should be radiometrically and geometrically corrected to enable adjacent files to be displayed simultaneously without obvious distinctions between them. In overall terms, the imagery must be free of the following types of errors:

• Misalignments in linear features (roads/curbs/building edges etc.) resulting from poorly stitched mosaics

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• Obvious seams between images • Blurred, out-of-focus, stretched, or poorly scanned imagery • Scratches, lint, blemishes or other artifacts introduced in the processing of the film or imagery • Stark changes in color balance and contrast • Stark shadows or bright spots in the imagery • Excessive shadowing in Ponderosa Pine areas resulting in imagery with more emphasis on the

shadows than the tree itself. • Buildings that obscure more than 25 percent of adjacent important features. Obscured valley

bottoms in the mountains. • Warped bridges/overpasses/viaducts

Imagery Scanning In the case of imagery acquired through traditional film-based methods, the imagery shall be scanned directly from negative film, at a resolution of 14 microns. The device used for scanning shall be a precision instrument designed for photogrammetric applications having an aperture capable of producing a scanning resolution of at least 10 microns, a geometric accuracy of 5 microns Root Mean-Square Error, and a capability of resolving sufficient levels of red, green, and blue to produce natural color imagery. Ground Control All horizontal and vertical control used to anchor the mapping product, and horizontal and vertical features contained within the final deliverable of the mapping product, must meet the APSRS Positional Accuracy Standards dated November 2015 along with the Map Modernization Guidelines and Specifications as published by the Federal Emergency Management Agency dated April 2003. In the event of a conflict between the two standards, the more stringent parameters will apply.

The aerial control panel positions will be reviewed by the City of Prescott prior to the placement of panel points. The City of Prescott reserves the right to place blind panels in order to verify the published accuracy. The control will utilize the Arizona State Plane Coordinate System, North American Datum of 1983 (1992), Central Zone (0202) horizontal datum and the North American Vertical Datum of 1988 (NAVD88) vertical datum using GEOID99.

NGS survey control stations/benchmarks shall be utilized in the control network for this project in addition to logging data at the City of Prescott Mingo Base Station. Information regarding the City base station can be found on the City website at: http://prescott-az.gov/services/engineering/base-stations.php. A sufficient number of control stations/benchmarks shall be included in the survey to meet the accuracy requirements of this project. The following NGS stations/benchmarks may be utilized:

Designation Horizontal Vertical Gates X X

Pioneer Park X X

http://prescott-az.gov/services/engineering/base-stations.php

http://prescott-az.gov/services/engineering/base-stations.php

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Prescott CORS ARP X X

Senator X X

Prescott X

Prescott South Base X

Watson X

E288 X

F28 X

L27 Reset X

RV 201 X

RV 207 X

RV 211 X

Camera Station Control Camera position (AZ State Plane coordinate system (units of international feet), NAD 83(1992), Central Zone (0202), Northing, Easting, and orthometric elevation (NAVD88)) shall be recorded at the instant of exposure with airborne GPS. Airborne GPS data shall be differentially corrected and organized as individual data sets grouped by corresponding film roll (or digital image groups if using non-film methods). The horizontal root-mean-square error (RMSE) of the airborne GPS control data shall not exceed 20cm (0.66 feet). The vertical RMSE of the airborne GPS control shall not exceed 30cm (0.98 feet). Final post-processed airborne GPS data shall be submitted to the City in a format mutually agreeable to the City and the Contractor. B. Image Rectification Digital orthophotograph production shall be produced consistent with the following requirements. a. Digital Orthorectified Images shall be 24-bit true color. Other available formats may be considered (e.g. color-infrared). b. Digital Orthorectified Image ground resolution shall be appropriate to the scale of imagery acquired (3 inch resolution). Control from the aerotriangulation and ground survey will be used to tie the digital images to actual ground coordinates. c. The rectification process shall involve solution of the appropriate photogrammetric equations for each pixel in the output image. It will not be permissible to solve photogrammetric equations at anchor points only and then warp the content of the original image between the anchor points. d. Digital Orthorectified Images shall be rectified to the Arizona State Plane Coordinate System, NAD 83(1992), Central Zone (0202), horizontal datum, with international feet as the unit of measure. e. Digital Terrain Model Vertical Accuracy - Vertical positional accuracy of the resultant DTM shall meet the vertical accuracy standards for elevation data as specified in the “ASPRS Positional Accuracy

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Standards for Digital Geospatial Data” (Edition 1, Version 1.0, - November, 2014). Testing of the data and a vertical accuracy statement shall be supplied as specified therein. The contractor must ensure that the data be capable of producing a one (1) foot interval contour map. f. Digital Orthorectified images shall be rectified to a composite Digital Terrain Model (DTM) developed by the vendor at appropriate resolutions and accuracy to develop the acquired imagery. g. Digital Orthorectified Image Horizontal Accuracy – Horizontal positional accuracy of the resultant imagery shall meet American Society of Photogrammetry and Remote Sensing (ASPRS) Class 1 Accuracy Standards for 1”=100’ scale mapping and meet National Standards for Spatial Data Accuracy (NSSDA) for a 1ft contour interval (RMSEz of 0.6 ft). The contractor will detail the methods used to ensure this level of accuracy in the Technical Proposal. h. Digital Orthorectified Image Tile Size – Orthorectified GeoTIFF files shall represent quarter section tiles cut at even quarter section lines with no overedge. The City will provide the contractor with a tile index indicating the tile layout and tile names. The index will be supplied as a shapefile suitable for loading into ArcGIS or Computer Aided Design Drafting (CADD) software. i. Orthorectified Image Chips shall be tonally balanced prior to generation of an image mosaic. Building tilt shall be corrected to the extent that other important features are not obscured. Relative join (misalignment) of transportation features between adjacent image chips/tiles shall be within the tolerance defined by the horizontal positional accuracy requirement set out above. Any methods of mosaicing orthoimagery to reduce relief displacement of buildings and terrain should be detailed in the technical proposal. j. File Naming Convention – The ortho tile filenames shall be derived from the tile index supplied to the contractor by the City. k. Coverage Area – The quoted price shall include all costs to provide complete coverage of the area shown in the coverage diagram of approximately 104 square miles included in Exhibit A. C. Quality Assurance The contractor shall perform quality assurance tasks on the orthorectified imagery to ensure the product meets all of the requirements for horizontal and vertical accuracy, image resolution, and image characteristics in this scope of work. Specific tasks to complete quality assurance will be detailed in the finalized scope of work. D. Project Deliverables The resultant imagery will be delivered on a timetable defined at the time of contracting. The deliverable products of this project will consist of the following items:

1. Flight Diagrams--A Flight Diagram plot and associated digital plot file shall be delivered that illustrates project area outline, photo identification (roll/exposure if film), and approximate location of photo centers.

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2. Aerial Control Panel positions—Provide locations of the proposed aerial panels for City review prior to establishing the aerial panels on the ground.

3. Aerial Control Panel Survey data and Ground Control Report—Provide final aerial panel point survey data in Point, Northing, Easting, Elevation, Description (P,N,E,Z,D) comma separated values format to the City, along with a PDF of ground control location specifics with images, sketches and notes from the locations in a report format that is sealed by an Arizona Registered Land Surveyor.

4. AGPS Track Plots--An Airborne GPS Ground Track Plot and associated digital plot file shall be

delivered. Ground track plot shall be created from airborne GPS coordinates recorded during flight.

5. Digital Orthorectified Images – Contractor shall deliver master copies of the orthophotographs

for the project area in uncompressed, ArcGIS readable, GeoTIFF computer file format on a mutually acceptable storage medium. The Contractor shall furnish geo-referenced world files for all ortho images.

6. Composite Elevation data developed for the DTM in the orthorectification process shall be

submitted as a deliverable in non-proprietary format suitable for use in ESRI GIS software and industry standard CAD software, such as a point DXF file. The contractor should list alternative file formats if available.

7. 1-foot contour interval file compatible with ESRI GIS software.

8. Federal Geographic Data Committee-compliant metadata for each tile.

E. Acceptance Criteria Imagery delivery must pass through a comprehensive evaluation and review process. This process will verify the positional accuracy of the data, and ensure its aesthetic and functional quality. The City of Prescott will oversee this quality control process using in-house resources. The City may reject any or all tiles that fail to meet the project’s positional accuracy or aesthetic and functional quality requirements. Prior to delivery of the product, horizontal positional accuracy testing will be performed following the methods proposed by the contractor in the technical proposal. The City of Prescott will review and test orthoimagery as it is delivered to ensure it meets the required accuracy standards and imagery qualities. Aesthetic and functional quality will be tested through a variety of qualitative and quantitative methods to ensure the imagery generally matches the aesthetic and functional quality of previous years of imagery.

F. Additional Scope of Work Documentation and Pricing Schedules

Additional correspondence that clarifies scope of work requirements and pricing schedules follow.

Submitted to: Prescott, AZ Attn: Cat Moody Historic Preservation Specialist GIS Coordinator 201 S Cortez Street Prescott, AZ 86303 Email: [email protected] Phone: 928-777-1309

Submitted by: Geophex, Ltd. 605 Mercury Street Raleigh, North Carolina 27603 Andrew Dawson President Email: [email protected] Ph: (919) 578-8857 (ext. 101) Fax: (919) 578-8849

Prescott, AZ

Orthophotography and Terrain Project

Geophex Ltd. Company Confidential

October 17, 2019 Quote# 20190121 Prescott, AZ

Re: Prescott Arizona Orthophotography and Terrain Project

To Cat Moody,

Geophex Surveys is pleased to offer Prescott Arizona our professional orthophotography and LiDAR/photogrammetry services which include 4-inch or 6-inch orthophotography, a new DTM and 2 ft contours. The project area encompasses the City of Prescott as shown in the diagram below and also includes an optional area on the western side.

Main project area shown in green (106mi²), Optional area shown in blue (7mi²)

Air Photo Acquisition

The aerial photography will be captured using a large format Vexcel UltraCam Falcon Prime digital aerial camera mounted to a fixed wing aircraft. Additional mounted sensors include airborne GPS and IMU which records the precise aircraft position and attitude during image acquisition. The average pixel resolution of the raw imagery will be matched to the resolution of the required orthophotography to ensure efficient flight planning and capture. In addition to the 4-inch and 6-inch resolutions requested, Geophex Surveys is also offering Prescott AZ 3-inch resolution as an option. See the table below for the aerial photography specifications. All photography will be acquired at 60% forward and 30% side overlap.

Flight Statistics Table (Entire project area)

Avg GSD No. of Flight Lines No. of Frames Flight Distance

3-inch 26 1783 269.7nm

4-inch 19 918 192.9nm

6-inch 13 436 141.6nm

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LiDAR Acquisition (Optional)

The optional LiDAR data will be captured utilizing an industry standard aerial survey grade Galaxy Prime LiDAR sensor. Two separate point densities are offered, 8ppm² and an optional 12ppm² which can be used to generate 2ft and 1ft contours respectively.

LiDAR Acquisition Flight Statistics (Entire project area)

Point Density Flying Height No. of Flight Lines Total Flight Distance

8ppm² 1250m 31 1300.9km

12ppm² 1125m 38 1599.6km

Ground Control

Ground control is fundamental to project accuracy, since the accuracy of all subsequent mapping is referenced back to the quality of the original ground control. These control points provide a precise measure of selected positions on the Earth’s surface within the project area.

To control the Prescott Arizona project, Geophex Surveys will utilize the existing control points from the previous project that we produced in 2016. The control points were established using industry standard photo-id methodology which uses easily visible and identifiable ground features that are considered to be permanent.

Each existing point will be examined to determine its viability, and if a control point is no longer useable due to changes in the landscape, a replacement will be surveyed if required. If the optional project area is selected, then a new control point will be established to ensure project-wide accuracy.

Project Accuracy

Utilizing our extensive experience in processing orthophoto projects, we have designed the Prescott AZ project to meet the highest accuracy standards, and to most effectively carry out the work using our efficient and proven methodology. All data will go through aerial triangulation processing.

Overall project accuracy is affected by several factors including flying height, pixel resolution, ground control, DEM, and the terrain of the project area. The following table shows the achievable accuracy of the various data components.

Prescott AZ Project Accuracy Table (RMSE)

GSD Ground Control

Aerial Triangulation

DEM (Photogrammetric)

DEM (LiDAR)

Contours Orthophotography

3-inch ≤1.5in (xyz) 3.0in (xyz) 6.0in (xyz) 4.0in (z) 6.0in (xy)

1ft 6.0in


2ft 8.0in


2ft 12.0in

Control Point Layout

Existing Control (blue), New Control for Optional Area (yellow)

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DTM/Contours

For the Prescott AZ project, Geophex Surveys is offering to either generate a new Digital Terrain Model or update the existing DTM. A new DTM can be created photogrammetrically or from LiDAR data, while an updated DTM will be generated photogrammetrically. For any photogrammetric processing, the DTM mass points and breaklines will be manually collected in 3D from the stereo models by our experienced operators, while the LiDAR based DTM will be generated from the processed and classified (to bare earth) LiDAR data. The DTM and contour options include:

Methodology Product

Photogrammetric

• Updating existing 2ft contours and new collection for extension area

• New project-wide 2ft contours


• Ortho-only DEM (no contours)

LiDAR • New project-wide 2ft contours


Orthophotography

Geophex Surveys is offering either 3-inch, 4-inch or 6-inch 4-band orthophotography for the project.

The orthophoto production process will rectify every frame of the 60% forward overlap photography. Every rectified frame is adjusted for color and contrast to provide project-wide radiometrically balanced imagery. During orthorectification and mosaicking, the imagery is examined for any artifacts resulting from optical and radiometric distortion, including such issues as structure/tree displacement (lean), hot spots, as well as tonal contrast between contiguous features on adjacent frames.

The final orthophoto product is comprised of center portions of every rectified frame as required to ensure continuous, seamless imagery across the project area.

Quality Control

Geophex Surveys performs rigorous QA/QC checks on all data before it is delivered to the client, and is solely responsible for all deliverables. Quality control is performed on all acquisition data prior to processing, and following each production step to prevent errors from being carried through to the final product. Quality Control includes the checking of:

• Aerial Photography

• Aerial Triangulation

• Digital Terrain Model

• Contours

• Orthophotography

• Final Deliverables

Schedule

• To be determined following confirmation of scope of work

Deliverables

• Orthophotography will be delivered in GeoTIFF format • DEM and Contours


Pricing

Product Base Area Additional Area Combined Total

Orthophotography

3-inch $37,993.86 $2,425.14 $40,419.00

4-inch $26,163.96 $1,670.04 $27,834.00

6-inch $20,279.56 $1,294.44 $21,574.00

Ground Survey

Ground Control $1,535.96 $98.04 $1,634.00

Photogrammetric DTM Products

Ortho DEM Update 3-inch (no contours) $5,399.36 $344.64 $5,744.00



Update DTM and 2ft contours $14,914.98 $952.02 $15,867.00

New DTM and 2ft Contours $43,906.46 $2,802.54 $46,709.00

New DTM and 1ft Contours $55,406.42 $3,536.58 $58,943.00

LiDAR DTM Products

New 2ft Contours at 8ppm² $37,429.86 $2,389.14 $39,819.00

New 1ft Contours at 12ppm² $42,155.24 $2,690.76 $44,846.00

• Each orthophoto option must be combined with ground survey costs and the appropriate photogrammetric DTM or LiDAR product.

• Applicable taxes not included

Sincerely, Andrew Dawson, President Geophex Surveys Tel: (919) 578-8857 ext. 101

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January 13, 2020 Attn: Cat Moody Historic Preservation Specialist GIS Coordinator 201 S Cortez Street Prescott, AZ 86303 Re: Geophex Surveys’ Response to Prescott 2020 Orthophoto Questions and Comments

Q1: New Datum Compatibility: In light of the National Geodetic Survey’s (NGS) proposed implementation of a new horizontal and vertical datum in the year 2022, Consultant should address this issue in the proposal, and propose solutions and proposed methodologies to ensure the aerial mapping data set delivered for this project can be properly transformed to the new datum in the future.

A1: The US National Geodetic Survey (NGS) will supply software (probably a new version of NADCON5) to convert coordinates from older datum to 2022. However, this software is meant to translate survey control translation only, not downstream mapping data sets (i.e. orthophotography, LiDAR DEM, Breaklines, etc.). Software such as GlobalMapper will provide a datum conversion solution for downstream products in time, but it has been our experience that the resulting conversion on mapping products is not as accurate as processing the data again from scratch using both control and AGPS/IMU data from the sensor in the native datum (i.e. 2022).

Q2: THE SURVEY CONTROL USED FOR THE LAST MAPPING WAS NOT REFERENCED TO THE CITY'S DATUM. CITY USES NAD83 (1992 ADJUSTMENT) AND NAVD88 UTILIZING GEOID99.(I think it was using the wrong GEOID model last time)

A2: Correct. The projection used in 2016 was Arizona State Plane Central Zone (FIPS_0202) and the vertical datum was NAVD88, but utilizing Geoid12B. To correct this with the 2020 project, our licensed Arizona land surveyor will perform office, tech and field time to ensure that the existing data is in the correct datum.

The additional cost to perform this work is $4,106.00

Q3: ACCORDING TO BRIAN FISHER, NGS GEODETIC COORDINATOR TO ARIZONA, SURVEY GROUND CONTROL SHOULD ALSO BE OBSERVED AND PROCESSED WITH OPUS PROJECTS TO ENABLE TRANSLATION OF THE DATA TO THE NEW 2022 DATUM IN THE FUTURE. INCLUDE OPTION TO ACCOMPLISH THIS TASK.

A3: New surveyed ground control will be processed using OPUS.

Q4: Ground Control - YOUR GROUND CONTROL NUMBER LOOKS PRETTY DARN LOW, SO WE WANT TO MAKE SURE YOU ARE TAKING THESE POINTS INTO ACCOUNT.

A4: Geophex Surveys has reviewed our ground control layout and the accuracies the City has outlined in the AT accuracy table shown below. We have determined that by adding two new control points and utilizing existing horizontal and vertical ground control established in 2016 (including the above translations as mentioned in A2), the COP/NGS monuments, and LiDAR points as vertical control, the project will meet the defined accuracy specifications. See adjacent diagram.

Original cost of ground control: $1,634.00

New cost of ground control: $2,661.00

Prescott 2020 Control Point Layout –

Existing (blue), New (yellow)


Q4a: I’VE ALSO INCLUDED THE ASPRS STANDARDS FOR YOUR REFERENCE

All horizontal and vertical control used as the basis for the mapping product, and horizontal and vertical features contained within the final deliverable of the mapping product, must meet the American Society for Photogrammetry and Remote Sensing (ASPRS) Positional Accuracy Standards for Digital Geospatial Data dated March 2015 (ASPRS Standards), along with the Map Modernization Guidelines and Specifications as published by FEMA dated April 2003. In the event of a conflict between the two standards, the more stringent parameters will apply. The required ground control accuracy is shown in the following table:

GROUND CONTROL ACCURACY

RMSEx and RMSEy (ft) RMSEz (ft)

0.125 0.075

A4a: Geophex Surveys acknowledges and accepts the required ground control accuracy shown above.

Q5: The aerial control panel positions will be reviewed by the City prior to the placement of panel points. The City reserves the right to place blind panels in order to verify the published accuracy. The control will utilize the Arizona State Plane Coordinate System, North American Datum of 1983 (1992), Central Zone (0202) horizontal datum and the North American Vertical Datum of 1988 (NAVD88) vertical datum using GEOID99. International feet shall be used as the unit of measure. The final, adjusted project control and panel point data shall be submitted to the City for review prior to the start of processing and preparation of mapping deliverables.

A5: Geophex Surveys acknowledges and accepts the above projection and project control deliverable.

Q6: NGS survey control monuments/benchmarks shall be utilized in the control network for this project in addition to logging data at the City of Prescott Mingo Base Station. Information regarding the City base station can be found on the City website at: http://www.prescott-az.gov/business-development/public-works-engineering/survey-information/. A sufficient number of control monuments/benchmarks shall be included in the survey to meet the accuracy requirements of this project. The following NGS monuments/benchmarks may be utilized:

Designation Horizontal Vertical

Gates X X

Pioneer Park X X

Prescott CORS ARP X X

Senator X X

Prescott X

Prescott South Base X

Watson X

E288 X

F28 X

K 27 X

L27 Reset X

RV 201 X

RV 207 X

RV 211 X

A6: Geophex Surveys acknowledges the available ground control and will utilize it in the course of the project. Geophex Surveys also acknowledges the requirement to log data at the City of Prescott Mingo Base Station.


Q7: In addition to the aerial control panels, a minimum of 20 check points shall be collected in accordance with the ASPRS Standards for use in calculating NSSDA accuracy statistics for x, y, and z.

A7: Geophex Surveys acknowledges and accepts the above check point requirement, and has defined a layout for the non-vegetated (20 points) and vegetated (5) checkpoints.

Due to the overall lack of heavy vegetation within the project area, the City of Prescott may opt to not include the vegetated checkpoints.

The additional cost for check points are as follows:

20 non-vegetated (NVA) points: $12,046.00

Optional 5 Vegetated (VVA) points: $2,933.00

Q8: Aerial Triangulation Requirements - Aerial Triangulation (A/T) accuracy for the project shall meet ASPRS 0.50-foot horizontal accuracy class, and 0.30 foot vertical accuracy class requirements as shown in the following table:

A/T ACCURACY

RMSEx AND RMSEy (ft)

RMSEz (ft)

0.25 0.15

A8. To achieve the ASPRS vertical accuracy requirements, it was determined that the LiDAR data is the source of vertical accuracy, as such the following A/T accuracies is sufficient to meet the project accuracy requirements.

A/T ACCURACY

RMSEx AND RMSEy (ft)

RMSEz (ft)

0.25 0.25

Q9: Vertical Accuracy - Digital Terrain Model Vertical Accuracy - Vertical positional accuracy of the resultant DTM shall meet ASPRS 0.30 foot vertical accuracy class as shown in the following table. Testing of the data and a vertical accuracy statement shall be supplied as specified therein.

Non-vegetated checkpoints (orange), Vegetated

checkpoints (pink)


The Consultant must ensure that the data be capable of producing a one (1) foot interval contour map.

A9. Geophex Surveys acknowledges and accepts the above vertical accuracy specification for the LiDAR.

Q10: Horizontal Accuracy - Digital Orthorectified Image Horizontal Accuracy – Horizontal positional accuracy of the resultant imagery shall meet ASPRS 0.50 foot horizontal accuracy class as shown in the following table. The Consultant will detail the methods used to ensure this level of accuracy in the Technical Proposal.

HORIZONTAL ACCURACY STANDARDS FOR GEOSPATIAL DATA

HORIZONTAL ACCURACY CLASS (ft)

ABSOLUTE ACCURACY ORTHOIMAGERY MOSAIC

SEAMLINE MISMATCH ≤ (ft) RMSEx & RMSEy ≤ (ft)

RMSEr ≤ (ft) HORIZONTAL ACCURACY AT

95% CONFIDENCE LEVEL ≤ (ft)

0.50 0.50 0.71 1.22 1.00

A10: Geophex Surveys acknowledges and accepts the above horizontal accuracy specification for the orthophotography.

Q11: Project Deliverables

Flight Diagrams—A Flight Diagram plot and associated digital plot file shall be delivered that illustrates project area outline, photo identification (roll/exposure if film), and approximate location of photo centers.

Acknowledged and Accepted.

Aerial Control Panel positions—Provide locations of the proposed aerial panels for City review prior to establishing the aerial panels on the ground.


Aerial Control Panel Survey data and Ground Control Report—Provide final aerial panel point and check point survey data in Point, Northing, Easting, Elevation, Description (P,N,E,Z,D) comma separated values (.csv) format to the City, along with a PDF of ground control location specifics with images, sketches and notes from the locations in a report format that is sealed by an Arizona Registered Land Surveyor.


AGPS Track Plots--An Airborne GPS Ground Track Plot and associated digital plot file shall be delivered. Ground track plot shall be created from airborne GPS coordinates recorded during flight.


VERTICAL ACCURACY STANDARDS FOR DIGITAL ELEVATION DATA

VERTICAL ACCURACY CLASS (ft)

ABSOLUTE ACCURACY ABSOLUTE ACCURACY

RMSEz, NON-VEGETATED

≤ (ft)

NVA @ 95% C.L. ≤ (ft)

VVA @ 95TH PERCENTILE

(ft)

WITHIN-SWATH HARD SURFACE REPEATABILITY (MAX DIFF) (ft)

SWATH-TO-SWATH NON-VEGETATED

TERRAIN (RMSDz) (ft)

SWATH-TO-SWATH NON-VEGETATED

TERRAIN (MAX DIFF) (ft)

0.30 0.30 0.59 0.90 0.18 0.24 0.48


Digital Orthorectified Images – Consultant shall deliver master copies of the orthophotographs for the project area in uncompressed, ArcGIS readable, GeoTIFF computer file format on a mutually acceptable storage medium. The Consultant shall furnish geo-referenced world files for all ortho images.


Composite Elevation data developed for the DTM in the orthorectification process shall be submitted as a deliverable in non-proprietary format suitable for use in ESRI ArcPro GIS software and Autodesk AutoCAD Computer Aided Design Drafting (CADD) software. The Consultant should list alternative file formats if available.


1-foot contour interval file compatible with ESRI ArcPro GIS software.


Federal Geographic Data Committee-compliant metadata for each tile, including horizontal and vertical accuracy testing statements as set forth in the ASPRS Standards.

Project level metadata is included in the original price of the project. To provide metadata for each tile, the additional cost will be $900.00.

NSSDA Accuracy Statistics report for x, y, and z.


Option for delineation of structures located within floodplains as per supplied shape file

The additional cost to perform this work is $1849.00.

Sincerely,

Andrew Dawson, President Geophex Surveys Tel: (919) 578-8857 ext. 101


January 15, 2020

Cat Moody Historic Preservation Specialist GIS Coordinator 201 S Cortez Street Prescott, AZ 86303

Subject: Revised Pricing table

To Cat Moody,

Please find our revised pricing table below that includes pricing for the 3-inch orthophotos and 12ppm² LiDAR products, the collection of structures within floodplains, and additional ground survey costs to meet the required City of Prescott project specifications.

Product Base flight Area Additional Area Option Total

Orthophotography

3-inch orthophoto $37,993.86 $2,425.14 $40,419.00

Structures within Floodplains $1,738.06 $110.94 $1,849.00

Ground Survey

Ground control $2,500.40 $159.60 $2,660.00

Translation $3,859.64 $246.36 $4,106.00

ASPRS NVA Check points (20) $11,323.24 $722.76 $12,046.00

ASPRS VVA Check points (5) $2,757.02 $175.98 $2,933.00

Meta Data

Meta Data $846.00 $54.00 $900.00

LiDAR

12ppm² LiDAR and new 1ft contours $42,155.24 $2,690.76 $44,846.00

Total Cost $109,759.00

• Applicable taxes not included

Sincerely,

Andrew Dawson, President Geophex Surveys

Email: [email protected] Tel: (919) 578-8857 ext. 101

cat.moody

Rectangle

high resolution orthorectified imagery lidar data

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