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Advanced Geographic Information Systems

Lab 8 Terrain

Analysis

http://bigthink.com/strange-maps Globalmapper.com

Spatial Analyst extension ESRI controls sets of tools and offers them as extensions that you must acquire separate licenses for. You are licensed to use the Spatial Analyst toolset with your student edition software, but you must enable the extension before using it for the first time:

From the Customize toolbar, choose Extensions… to open Extensions window. Check boxes next to all extensions (but especially Spatial Analyst) and click Close to enable licenses.

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Question: What’s up with the

representative fraction love-fest?

Representative

fractions are so hip

and modern, just like

the slide rule and

abacus! They’ll never

become irrelevant.

1 : 2000 1 : 50,000 1 : 30,000

1 : 70,000 1 : 600

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1 : 3500 1 : 16000 Not True

Always True

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Lab 5 fine-tuning symbology

Which are the active polygons?

Semi-transparent fill demonstrates which polygons are active

Remove unnecessary layers to maintain focus on relevant data

OK:

Awesome:

Awkward to have irregular

values span multiple data

frames. Viewer has to

mentally isolate sections of

scale bar, do some

subtraction, visually

skootch things around…

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Lab 6 awesomeness:

Lab 6 awesomeness:

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Gridding on 30m DEM artifact of AGRC processing.

To get your hands on clean 30m DEM data retrieve directly from

USGS seamless server

Note:

Lab 8

Terrain Analysis Task 1 Define a Watershed Task 2 Stream order classification Task 3 Slope and curvature analyses Zonal Statistics as Table

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Lab 8 Task 1

Watershed delineation

How can we define a watershed using raster cell values representing elevation?

ArcGIS defines the watershed boundary by identifying cells with zero flow coming into them

Watershed Delineation:

How can we define a watershed using raster cell values representing elevation?

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Using Flow Accumulation to define watershed boundaries

3 1 0 0 1

2 1 0 0 1

2 1 0 0 1

2 1 0 0 1

3 1 0 0 1

2 0 0 0 1

5 2 1 0 0 1

2 1 0 0 1

3 1 0 0 1

Watershed Delineation:

Watershed Delineation:

Boundary is defined by the pour point.

Gsshawiki.com

Pour Point

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Lab 8 – watershed delineation

Lab 8 – watershed delineation

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Watershed Delineation:

DEM Fill Flow Direction (directional symbology or start over) Flow Accumulation (input flow direction) (integer) Naming convention: DEM10m_fd DEM10m_fa DEM10m_hs DEM10m_slp Slope hillshade_dem flowdir_dem Flow_Accumulation

Lab 8 Task 2

Flow accumulation

Stream order

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Flow Accumulation

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Lab 8 – stream orders • Provide table with

lengths of each order (units)

• In write up, defend reasonableness of stream network (include threshold value)

The created drainage network will depend on:

• DEM resolution (quality)

• pour point location • threshold value

Lab 8 Task 3

Slope and Curvature analyses

Summarizing watershed characteristics

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Lab 8 - Slope

Lab 8

http://www.spatialanalysisonline.com/output/html/Curvatureandmorphometricanalysis.html

Task 3: Curvature

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Zonal statistics

76.5 %

Watershed boundary

Slope raster

Inputs

Lab 8

Big Cottonwood Canyon watershed

Mean Minimum Maximum Standard Deviation

Slope (% Rise) 56 1 397 12

Planform Curvature (units?)

-3.3 -15 14 2.7

Profile Curvature (units?) -4.7 -8 12 1.6

Task 3

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Lab 8 – surface analyses

Upload URL to Canvas before lab next week

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Where to lines of equal pressure go to relax?A. In ISO – bars (In Search Of isobars)

• Formal map: convince us watershed delineation was done correctly (compare to downloaded shapefile, compare [close up] to topo map)

• Write up: brief statement that convinces delineation was done

correctly (discuss/show screenshot and defend choice of pour point location?)

• Define tools

• Fill • Flow direction • Flow accumulation What does it mean (generally and what do output cell values represent [units?] and how does it calculate from elevation cell values?)

Lab 8 – Task 1

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Lab 8 – watershed delineation

Lab 8 – stream orders

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Discussion The lower the threshold value that was used, the more stream channel length that was created. Using a threshold value of 1250 created a total stream length of 245.94 km but using a threshold value of 1500 created a total stream length of 202.32 km. When the created drainage network was overlayed on top of a USGS topographic map there were a couple of differences:

streams were created that did not exist on the topo map; and, some created streams did not extend all the way in elevation as some of the streams from the topo map

The created drainage network will depend on:

• DEM resolution (quality) • pour point location • threshold value

Lab 8 – stream order

Lab 8 – surface analyses

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Lab 8 – surface analyses

• Provide captioned screenshots of Slope, PrC, PlC results

• Provide table with min, max, mean, and SD for slope, planform C, profile C (units!)

• Define tools:

• Zonal Statistics • Slope • Planform Curvature • Profile Curvature What do these mean, what do output cell values represent [units?], how are they calculated from elevation cell values?

Lab 8 – Task 3

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Planform Curvature Light cells - water flow is divergent Dark cells – water flow is convergent

Profile Curvature Light cells – water flow is decelerating Dark cells – water flow is accelerating

Lab 8 – surface analyses