digital elevation models · jackson school of geosciences, university of texas at austin...

Geo327G/386G: GIS & GPS Applications in Earth SciencesJackson School of Geosciences, University of Texas at Austin

Digital Elevation Models

National Elevation Dataset

10-Oct-19 1


Data Sets US DEM series7.5’, 30’, 1o for conterminous US7.5’, 15’ for Alaska

US National Elevation Data (NED) GTOPO30 Global Land One-kilometer Base Elevation (GLOBE) ETOPO2 Shuttle Radar Topographic Mission (SRTM) Advanced Spaceborne Thermal Emission and Reflection

Radiometer (ASTER) LIDAR data (TNRIS and other sources)Custom models from stereo photo pairs – photogrammetry –

SfM-Structure from MotionOthers -

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US 1o DEMs

~90 meter resolution

WGS72 or WGS84 datum

Decimal seconds (!) in older .dem format

Elev. in meters

Obtain via FTP

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ftp://edcftp.cr.usgs.gov/pub/data/DEM/250/


US 7.5’ DEMs

NAD83 (or NAD 27)

Resolution 30 (or 10) meters

UTM projections

Entire US available

1:130,00 as captured

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http://www.gisdatadepot.com/dem/


Data Sets

US 7.5’ DEMs: detailed view


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Data Sets

US 7.5’ DEMs: at 1:24,000


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US National Elevation Data (NED)

Seamless data set for US and territories

1 Arc Second (30 m) resolution

NAD83, decimal degrees

Distribution very slick

Available in Arc .grd format

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http://edcnts12.cr.usgs.gov/ned/default.htm

http://seamless.usgs.gov/


GTOPO30

USGS Global 30-Arc Second DEM

Completed 1996

Horizontal grid spacing ~ 1 km

21,600 rows x 43,200 columns

WGS84 and “sea level” datums

Data are in decimal degrees and meters above S.L.

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GTOPO30

30o x 50o Data Tiles, EROS Data Center or via FTP

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http://edcdaac.usgs.gov/gtopo30/gtopo30.html

ftp://edcftp.cr.usgs.gov/pub/data/gtopo30/


GTOPO30 in ArcMap

Load in band-interleaved-by-line (.bil) format

Convert .bil to .grd (Spatial Analyst)

-16 bit binary integer data converted to ASCII

Use map calculator to restore negative values and convert –9999 (no data) cells to null.

Details are available

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http://www.geo.utexas.edu/courses/371c/Labs/Software_Tips/GTOPO30_import.htm


GTOPO30 tiles in ArcMap

1:10,000,000 (as captured) 100 meter classes

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GTOPO30 resolution: S. Africa

1:2,000,000

1:1,000,000

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The Global Land One-km Base Elevation

G.L.O.B.E. – NOAA data

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The Global Land One-km Base Elevation

GLOBE 1 completed 1999

90o x 45o tiles

WGS84, decimal degrees

Import in ArcMap exactly like GTOPO30

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http://www.ngdc.noaa.gov/seg/topo/globe.shtml

http://www.ngdc.noaa.gov/seg/topo/gltiles.shtml


ETOPO2

NOAA global relief (land & oceans)

Gridded at 2 minute resolution (~4 km): 10800 columns x 5400 rows

Subsets can be extracted from CD in a variety of formats

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ETOPO2

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ETOPO2

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Shuttle RadarTopographic Mission

10-day mission in Feb. 2000 to map earth’s topography at 30 m x, y resolution and ~ 16 m in z

Topography derived from radar interferometry

One of two best global data sets to date

interferogram

Images courtesy of NASA http://www.jpl.nasa.gov/srtm

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http://www.jpl.nasa.gov/srtm


SRTM Coverage

~ 60oN to 56oS latitude

~ 80% of land surface

Images courtesy of NASA http://www.jpl.nasa.gov/srtm

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http://www.jpl.nasa.gov/srtm


SRTM Data Availability

1-arc second (30 meter) SRTM data of the continental US available via the USGS EDC Seamless Distribution SystemUp to 30 degree squares of raster data (1.6 gigabytes), in 100

megabyte sized files, can be downloaded at no charge.

As new 3-arc second (~90 meter) international continental datasets are available, USGS will distribute via the Seamless Data Distribution System - Enhanced.

Higher resolution (30 meter) international data are available via special request (?)

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http://seamless.usgs.gov/viewer.htm


ASTER DEMs

Advanced Spaceborn Thermal Emission and Reflection Radiometer

Used for surface temperature, reflectance and elevation

See ASTER data site for details

30 meter–resolution DEMs are available for registered users (i.e. GDEM) – global data set!

If not GDEM then data conversion for individual tiles to ArcInfo is required

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http://asterweb.jpl.nasa.gov/

http://asterweb.jpl.nasa.gov/data.asp

http://asterweb.jpl.nasa.gov/gdem.asp

http://www.geo.utexas.edu/courses/371c/Labs/Software_Tips/AsterDEMs.htm


ASTER GDEM

Global 30 meter postings!

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Single ASTER Tile Example

Lascar volcano, Chile

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LIDAR – LIght Detection And Ranging

= “Laser Radar”: two-way ranging technique using a laser scanner

Airborne LIDAR

“Scanning” (Ground-based) LIDAR

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http://www.jsg.utexas.edu/galleries2/pages/140.html





Airborne LIDAR

From Gibeaut, 200410-Oct-19 25

http://www.beg.utexas.edu/mainweb/presentations/2004_presentations/pptques/gibeaut1_0304.ppt


Airborne LIDAR

Requires

Precise positioning for aircraft (DGPS ground and air)

Laser ranges & scan angles

Platform position (yaw, pitch, roll of aircraft)

Produces

Swaths 100’s meters wide

Accuracy of 1-4 cm in x,y,zA – Laser head

B – Control rack

BEG’s (old) LIDAR unit in a Cesna 206

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Matagorda Island LIDAR

From Gibeaut, 2004

Contour interval = 25 cm!

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http://www.beg.utexas.edu/mainweb/presentations/2004_presentations/pptques/gibeaut1_0304.ppt


Airborne LIDAR in ArcGIS

1. Convert LAS file(s) to “Multipoint” feature class

2. Use Multipoint to create a TIN “Terrain”

3. Covert TIN to DEM (DTM)

Terrain Model (TIN) hillshade of DEM (raster)

Data from TNRIS

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Application: Airborne LIDAR slope mapping

Mapping of geologic units and faults by changes in slope, e.g. central Texas hill country

Cretaceous Glen Rose and Walnut Formations (carbonate rocks)

Slope Map hillshade of DEM (raster)

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Terrestrial LIDAR

From Belian et al., 2005

Rapid, quantitative characterization of outcrops

2,000 pts/sec, 10-15 mins/scan

“Point clouds” rendered with software

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http://www.beg.utexas.edu/staffinfo/pdf/bellian_jsr_2005.pdfl

http://www.optech.ca/Products/ilris.tif

http://www.optech.ca/Products/ilris.tif


360o Cave Image

From Gary

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http://www.geo.utexas.edu/zacaton/3D_Mapping/images/cuarteles_intensity_images.htm


Terrestrial LIDAR Applications

From Belian et al., 200510-Oct-19 32

http://www.beg.utexas.edu/staffinfo/pdf/bellian_jsr_2005.pdfl


Scanning Lidar on robotic rover

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Photogrammetry: “Structure from Motion: SfM”

Unmanned Aerial Vehicles (UAVs) and photogrammetry software

Google Earth image

274 stitched UAV images

1.5 cm resolution!

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Custom Photogrammetry

274 stitched UAV images

From Fonstad et al., 2013SfM = “Structure from Motion” photogrammetry

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digital elevation models · jackson school of geosciences, university of texas at austin...

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