User:Ikonor/DE:CGIAR-CSI SRTM 1/2 Pixel Versatz
Jump to navigation
Jump to search
Fragen/Unklarheiten
- Pixel-Darstellung bei PixelIsPoint? (halbes Pixel verschoben, so dass Rastergitter/Punktkoordinaten in Pixel-Mitte?)
- ArcASCII corner/center = GeoTIFF PointIsPixel/PointIsArea?
- CGIAR ArcASCII x/yllcorner vs. GeoTIFF AREA_OR_POINT=Area
- cgiar.org GeoTIFF 6001 Pixel, in readme.txt aber "All GeoTiffs with 6000 x 6000 pixels"
CGIAR-CSI SRTM 90m v4.1 Downloads
http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp
readme.txt Auszug (in alle Downloads gleich):
Version 4.1 has the following enhancements over V4.0:
- All GeoTiffs with 6000 x 6000 pixels.
ArcASCII
ftp://srtm.csi.cgiar.org/SRTM_v41/SRTM_Data_ArcASCII/srtm_37_05.zip
srtm_37_05.asc Header:
ncols 6001
nrows 6001
xllcorner -0.00041661826815287
yllcorner 34.999583454375
cellsize 0.00083333333333333
NODATA_value -9999
"gdalinfo srtm_37_05.asc" Auszug:
Size is 6001, 6001
Origin = (-0.000416618268153,40.000416787708311)
GeoTiff
CGIAR-CSI (USA)
ftp://srtm.csi.cgiar.org/SRTM_V41/SRTM_Data_GeoTiff/srtm_37_05.zip
"gdalinfo srtm_37_05.tif" Auszug:
Size is 6001, 6001
Origin = (-0.000416618268153,40.000416787708332)
Metadata:
AREA_OR_POINT=Area
JRC (IT)
ftp://xftp.jrc.it/pub/srtmV4/tiff/srtm_37_05.zip
"gdalinfo srtm_37_05.tif" Auszug:
Size is 6000, 6000
Origin = (0.000000000000000,40.000000000000000)
Metadata:
AREA_OR_POINT=Area
SRTM
USGS GeoTiff
http://earthexplorer.usgs.gov/ "SRTM Void Filled" (90m v2)
"gdalinfo n39_e003_3arc_v2.tif" Auszug:
Size is 1201, 1201
Origin = (2.999583333333333,40.000416666666666)
Metadata:
AREA_OR_POINT=Point
DTED_OriginLatitude=0390000N
DTED_OriginLongitude=0030000E
DTED_...
PixelIsArea vs. PixelIsPoint
- GeoTIFF spec: Raster Space
- GDAL Metadata: AREA_OR_POINT=Area|Point
- GeoTIFF FAQ: What is the effect of PixelIsArea vs. PixelIsPoint?
- Esri ASCII-Raster-Format
- XLLCENTER vs. XLLCORNER
- CGIAR-CSI SRTM FAQ: What is the point of origin and placement of a pixel in the dataset?
Andere sind auch verwirrt
- GDAL RFC 33: GTiff - Fixing PixelIsPoint Interpretation
- naviboard.de Thread
- Blog: GeoTIFF and Off-By-One
- CGIAR-CSI:
- Version 3 differs from Version 2 with a ½ grid pixel shift
- Version 4 differs from Version 3 with a ½ grid pixel shift which definitively solves this confusion.
- All GeoTiffs with 6000 x 6000 pixels. (Version 4.1, readme.txt)
Sampling vs. Averaging
- CGIAR-CSI: averaged
- CGIAR-CSI gibt als Quelle ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM3/ an (nicht mehr erreichbar) -> siehe Version 2, nasa.gov unten
- USGS: subsampled
- http://earthexplorer.usgs.gov/ "SRTM Void Filled", v2 in Dateiname (n39_e003_3arc_v2.tif) -> siehe Version 2, usgs.gov unten
Versionen und Quellen:
- Version 2, 3” world (SRTM_Topo.pdf)
- subsampled: http://seamless.usgs.gov/ (existiert nicht mehr)
- averaged: ftp://e0srp01u.ecs.nasa.gov/srtm/ (nicht mehr erreichbar)
- Version 2.1 averaged: http://dds.cr.usgs.gov/srtm/version2_1/
- "Version 2.1 is a recalculation of the SRTM3 (nominal 90 meter sample spacing) version made by 3x3 averaging of the full resolution edited data" (What_are_these.pdf)
- Version 3.0 (SRTM Plus): http://e4ftl01.cr.usgs.gov/SRTM/ (.hgt)
- SRTMGL3: averaged
- SRTMGL3S: sub-sampled