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INMAP 2005 Elevation Datasets. Anna Radue University Information Technology Services (UITS) Indiana University. INMAP05 Elevation Data. Created from 2005 Indiana orthophotography imagery collected in March & April, 2005 65,670 DEM ERDAS *.img files (~200 GB) 34,161 stple images

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inmap 2005 elevation datasets

INMAP 2005 Elevation Datasets

Anna Radue

University Information Technology Services (UITS)

Indiana University

http://gis.iu.edu [email protected]

inmap05 elevation data
INMAP05 Elevation Data
  • Created from 2005 Indiana orthophotography imagery collected in March & April, 2005
  • 65,670 DEM ERDAS *.img files (~200 GB)
    • 34,161 stple images
    • 31,509 stplw images
  • 800 x 800 pixel *.img images
  • 2.78 MB *.img file and 0.3 MB *.rrd

http://gis.iu.edu [email protected]

dem and dsm image properties
DEM and DSM Image Properties
  • Cell size (X,Y): 5 feet, 5 feet(4,000 ft x 4,000 ft)
  • Source Type:
    • Continuous
    • 32 bit floating point
    • Uses 4bytes/pixel for storage
    • Supports decimals
  • Elevation Units: Feet

http://gis.iu.edu [email protected]

accuracy
Accuracy
  • Horizontal
    • Better than 5 feet at 95% conf level for 1 FT counties
    • Better than 2.5 feet at 95% conf level for 6 inch counties
  • Vertical
    • Compiled to meet 6 foot vertical accuracy at 95% conf level
    • Suitable for automated compilation of 10ft contours

http://gis.iu.edu [email protected]

2 ft contours
2 Ft Contours
  • Higher accuracy contours can be produced but only with additional ground control points, re-triangulation of the datasets, and stereo-compilation of breaklines as required.
  • Dearborn County and City of Bloomington have purchased

http://gis.iu.edu [email protected]

32bit floating data
32bit Floating Data
  • Challenge to load to ArcSDE geodatabase raster dataset
  • Required using ArcSDE 9.2 sderaster
  • Tried loading using Python scripting, but memory leaks with ArcGIS 9.1; loading failed after loading ~200 images

http://gis.iu.edu [email protected]

arcsde raster dataset
ArcSDE Raster Dataset
  • Valuable to load images to raster dataset as any misaligned or corrupt images found.
  • Sderaster command
    • loads only TIFF or BSQ files
    • Exported *.img files to Geotiff format
    • Loaded with command line using LZ77 (lossless) compression
    • Could visualize entire state
    • Geotiff files available for download from ISDP

http://gis.iu.edu [email protected]

dem index
DEM Index

http://gis.iu.edu [email protected]

challenge create single statewide dataset
ChallengeCreate Single Statewide Dataset
  • Mosaic stpl *.img images by county
  • Reproject to UTM
    • Cell size ?
    • Resampling method?
    • Subset to remove invalid DNs and no data areas
  • Load Data to ArcSDE raster dataset
  • Archive county mosaics on ISDP

http://gis.iu.edu [email protected]

cell size
Cell Size
  • STPL imagery 5 ft (1.524m) pixels
  • UTM selected 1.5 meters to most closely approximate spatial resolution of original imagery
  • Changing to 1 meter pixels would more than double the size of the imagery

http://gis.iu.edu [email protected]

determining pixel size
1m 1m 1m

5ft

5ft

1m

5ft

1m

5ft

1m

Determining Pixel Size

1.5m

1.5m

1.5m

1.5m

32 bit floating data stores 4 bytes/pixel

4 pixels/image * 4 bytes/pixel = 16 bytes/image

9 pixels/image * 4 bytes/pixel = 36 bytes/image

36/16 = 2.25

http://gis.iu.edu [email protected]

pyramid resampling methods
Pyramid Resampling Methods
  • Nearest Neighbor
    • Does not create new values
    • Categorical data – landuse
    • Can be used on continuous data but the results can be blocky
  • Bilinear Interpolaton
    • Creates new values
    • Used for elevation data
  • Cubic Convolution
    • Good for smoothing continuous data
    • Computationaly intensive

http://gis.iu.edu [email protected]

results from resampling
Results from Resampling

Gray Valid DN

Red No Data (0 DN)

Green Invalid DNs

Result bilinear interpolation

http://gis.iu.edu [email protected]

subsetting
Subsetting
  • Difficult for border counties, required multiple subsets
  • Important to subset to create images which align with raster dataset grid
  • Use coordinates for whole pixel values

http://gis.iu.edu [email protected]

county dem mosaics utm stpl
County DEM MosaicsUTM & STPL
  • Large files 1-3 GB
  • Stateplane
    • IMAGINE, tiled
    • No NoData pixels
  • UTM
    • Striped, GeoTIFF
    • Border Counties have NoData (0)

http://gis.iu.edu [email protected]

tiff format 6 0 spcs
TIFF Format 6.0 Spcs

Tiled 64x64 pixels

Striped - default

http://gis.iu.edu [email protected]

tiff tile format
TIFF Tile Format
  • Image is broken in square tiles (64x64 pixel), each tile is loaded separately into memory and can be accessed independently of other tiles
  • All tiles in an image are the same size (4096 pixels/tile)
  • Border tiles are padded to the tile boundaries
  • If image is 800 pixels wide, then the image is stored as 13 tiles wide - 32 pixels are added for padding to fill rightmost column of tiles 800/64 = 12.5 832/64 = 13
  • Good viewers do not display pixels used for padding
  • Method used by ERDAS IMAGINE for .img files
  • Good for high-resolution, large images
  • Applications can access imagery more efficiently
  • Better compression with this format
  • ArcGIS 9.1 & 9.2 support, earlier versions do not
  • Other software may not support?

http://gis.iu.edu [email protected]

image information erdas imagine inmap 2005 dem img tiled format
Image Information ERDAS IMAGINEINMAP 2005 DEM.img – Tiled Format

64 pixel x 64 pixel tiles

13 tiles/image

http://gis.iu.edu [email protected]

striped geotiff created from tiled dem img
Striped Geotiff created from tiled DEM.img

Stripe format

800 pixels x 8 pixelstrip

100 stripes/image

http://gis.iu.edu [email protected]

size of striped and tiled images
Size of Striped and Tiled Images

*IMG (tiled) format (800x800 pixels): 2,782,240 bytes

TIF (stripe) format (800x800 pixels): 2,561,691 bytes

800x800 4bytes/pixel : 2,560,000 bytes/image

IMG (tiled) format (832x832 pixels): 2,785,163 bytes

TIF (stripe) format (832x832 pixels): 2,777,675 bytes

TIF (tiled) format (832x832 pixels): 2,773,747 bytes

832x832 4bytes/pixel: 2,768,896 bytes/image

* Format of INMAP05 DEM Imagine files

http://gis.iu.edu [email protected]

tiff format summary
TIFF Format - Summary
  • IMAGINE file format is tiled
  • Default output TIFF format for ERDAS IMAGINE is striped unless preferences changed
  • Tiled image has padding if rows and columns not divisible by 64 – increases image size without adding information
  • Tiled Tiff – compresses better with Winzip than striped image
    • Clark County DEM
      • Striped: 2.007 GB
      • Tiled: 1.759 GB

http://gis.iu.edu [email protected]

acknowledgements
Acknowledgements
  • ArcSDE/Oracle ConsultantMannion Geosystems, LLC
  • Data Management Support, UITS
    • Michael Halla, Manager
    • Stephanie Snider
  • Research and Technical Services, UITS
  • Digital Storage Services Group, UITS

http://gis.iu.edu [email protected]

uitsgis@indiana edu

[email protected]

Access data

http://gis.iu.edu

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