A Comparison Study Between Ground- Truth

Temperature Data of Mitchell Lake and the Temperature

Data Obtained Using MODIS Satellite Images.

Amber PatrickErin Manitou

Department of Earth and Environmental Sciences

The University of Texas at San AntonioEES 5053, Remote Sensing

Fall, 2006

Outline

ObjectivesBackground Information

Mitchell LakeMODIS dataGround Truth Data

MethodsResultsConclusion

Objectives

To assess whether or not MODIS images are a quality indicator of lake temperatureTo compare the remotely sensed data with ground-truth data for comparison

Mitchell Lake

Elm Creek

Cibolo Creek

Upper Salado Creek

Martinez Creek

Medina River

Culebra Creek

Calaveras Creek

Upper San Antonio RiverLower Salado Creek

Lower Leon Creek

Upper Leon Creek

Medio Creek

Lower San Antonio River

Cibolo Creek

Atascosa River

San Geronimo

Atascosa River

Bexar county map showing watershed and Mitchell Lake. Major Highway

systems are also shown.

Coordinate System: NAD 1983 State Plane Texas South Central FIPS 4204

Feet

Mitchell Lake Background Information

Mitchell Lake LogisticsLocated SW of city of San AntonioCoordinates: 29º32’N Latitude and -98º28’W Longitude.Average lake depth is less than 8 feet 600 acres body of water centered on 1,300 acres of wetlandsOne of the two natural lake in state of Texas

Mitchell Lake Background Information

Mitchell Lake as Sludge LagoonLake was damned in early 1900’s and received raw sewage from the city of San Antonio area until 1930’sObviously, poor water quality resulted with problems such as odorous algal blooms and sever eutrophication of the lakeFrom 1987 until present time, the lake is receiving only treated water from the Leon Valley Water Treatment Facility

Mitchell Lake Background Information

Mitchell Lake as Wildlife RefugeActs as a bird sanctuary for over 300 species of migratory birds that pass through the area each year Lake is owned by SAWS, but is overseen by National Audubon Society

MODIS Background Information

MODIS (Moderate-resolution Imaging Spectroradiometer) was launched on board the Terra satellite (sun-synchronous) in 1999Terra orbit is north to south so that it crosses the equator in the morning. Terra passes over Mitchell lake at approx. 1:30 am and 1:30pmAcquires data in 36 spectral bands ranging in wavelengths from 0.4μm to 14.4μm Swath dimensions are 2,300km x 10kmSpatial resolution of 250m (bands 1-2), 500m (bands 3-7), 1000m (bands 8-36)Radiometric sensitivity of 12 bits

Ground-Truth Data Data acquisition began August 21, 2006 Data acquired by Dr. Murray, Dr.Bodour and Magdalis Morales (undergraduate student) Data acquired using a Troll 9000Pro XP probeThe probe is located on the south rim of Basin #5 approximately 5 feet under the surface.

Location of Probe

*

Methods

Images obtained from the EOS gateway websiteWe used the MODIS reproject tool to convert the downloaded files to .tif files for use in ENVIIn ENVI, we used band math equation to convert pixel value to degrees K

Methods Continued….

Density slice was applied to each image with 25 different temperate ranges from 286 K to 332 KNew color every 3 degrees K

Methods

ROI

An ROI was made of Mitchell Lake and applied to each imageTemperatures compared with ground-truth data

Results

758595

105115

Temp (degrees F)

1 2 3 4 5 6 7 8 9

Pixel Number

Temperature data for Day 228 (8-16-06) per pixel

Day

Night

Results…

70

80

90

100

110

Temp (F)

222 223 225 228 229 230 232 237 239

Julian dates

Temp data for Pixel #4

Day temp Night temp

Conclusions

Lack of consistent data proved to be a problem in accurately comparing remotely sensed products with ground-truth dataGround truth data not compatible with remotely sensed data due to different location of probeMODIS doesn’t seem to be useful for gaining accurate temperature data for a water body as small as Mitchell Lake.

Factors Affecting Project Results

Cloud covering area of interest. (We were not able to use Aqua data as originally planned due to excessive cloud cover.)Probe location too deep for accurate comparisons to be made.MODIS images has too big of a spatial resolution for such a small subject area. Landsat 7 has a better spatial resolution(15m).Images from other more appropriate sensors are costly, MODIS images are free from the EOS Gateway.

ReferencesAranoff, S. 2005. Remote Sensing for GIS Managers. ESRI Press. Redlands, California. Branom, J., Sarkar, D. 2004. Phosphorus bioavailability in sediments of a sludge disposal lake. Environmental Geosciences. V.11, No.1.42-52.MLWS. 2002-2005. http://www.mlws.org. Mitchell Lake Wetlands Society, San Antonio, Texas.Oesch, D. C., Jaquet, J. M., Hauser, A., Wunderle, S. 2005. Lake Surface water temperature retrieval using advanced very high-resolution radiometer and Moderate Resolution Imaging Spectroradiometer data: Validation and feasibility study. Journal of Geophysical Research. 110: C12014.SAWS. 2000. Mitchell Lake Master Implementation Plan. San Antonio Water Systems, San Antonio, TX.Simpson, N., Sarkar, D., Datta, R., Sharma, S. 2006. Effects of Sewage Sludge Disposal on Metal Content in the Sediment and Water of Mitchell Lake, San Antonio, Texas. Bull. Environ. Contam. Toxicol. 77:104-111. Metal Content in the Sediment and Water of Mitchell Lake, San Antonio, Texas, USA. Environ. Contac. Toxicol. 77: 104-111.Vertucci, F., Likens, G. 1989. Spectral reflectance and water quality of Adirondack mountain region lakes. Limnol.Oceanogr. 34 (8): 1656-1672.Waclawczyk, J. L., 2004. Yellow River Delta Morphology Over Time: A Remote Sensing Spatial Study Utilizing Historical MODIS Images. RS 5053, Fall 2004.Williams, M. C., Campos, J., 2005. MODIS/Terra Urban Heat Island Temporal Formation and Dissipation in San Antonio, Texas. RS 5053, Fall 2005.