Changes between Version 2 and Version 3 of Processing/PixelSize

Timestamp:

Feb 4, 2008, 7:08:03 PM (17 years ago)

Author:

mggr

Comment:

--

Processing/PixelSize

@@ -2 +2 @@
 
 == Quick reckoner ==
-|| '''Altitude (ft)''' || '''Pixel size (m)''' ||
-|| < 3000 ft           || 1m ||
-|| 3000 - 4000 ft      || 2m ||
-|| 4000 - 6000 ft      || 2.5m ||
-|| 6000 - 8000 ft      || 4m   ||
-|| > 8000 ft           || 5m   ||
+|| '''Altitude over ground (ft)''' || '''Pixel size (m)''' ||
+|| < 3000 ft                       || 1m ||
+|| 3000 - 4000 ft                  || 2m ||
+|| 4000 - 6000 ft                  || 2.5m ||
+|| 6000 - 8000 ft                  || 4m   ||
+|| > 8000 ft                       || 5m   ||
 
-== More info ==
+Note this is the altitude over the ground, not the altitude from GPS (which is over the spheroid and takes no account of local terrain variation).
+
+Logsheets provided by ARSF contain the altitude from GPS.  One must compensate for the average terrain height when using the reckoner above.  For example, if your data is over coast areas and thus at sea level, the numbers are fine as is.  If your data is over a mountain valley, one should subtract the average height of the terrain from the logsheet altitude, then use that ground-altitude in the table above.
+
+== azgcorr-based pixel size ==
 
 To get a (still approximate) "best" pixel size, run through azgcorr once and there's a block in the azgcorr output: