08.08.2008, 15:15
lowfighter Wrote:Hey thanks M8s for help! I rushed to check and setting the number smaller will get different output maps. However I found that a correct size was 0.0018 . I checked using google earth and the latitude and longitude "box" of the srtm data (just one srtm block). The vertical dimension measured on googleearth was 556 Km
The size of the image I got with 0.0018 scaling was 2764 by 2764 pixel. So the vertical dimension image was 2764*200=552800 or approx 553 Km
So the error was of about 3 Km in 550 Km...
EDIT:hm I don't quite get it, just realised on google that the srtm data is not a square so if I measured the horisontal dimension I got a much smaller distance (358 Km). However the microdem image is square so I don't undertsand, or maybe I understand that one has to correct the output image in one dimension (vertical or horisontal) too? Am I right? Then maybe it's now clear why I got the scale "right" with 0.0018 and you got it right with a different value?
On the vertical correction issue.
I noticed the same thing while working my Denmark map, it came out seemingly "squashed". I figured that since the data most likely are based on views from GEO, a good approximate correction factor would be the mean latitude of the area in question. Tried correcting (or streching) my initial maps (_c and _h) for 56 degrees (stretch vertically be 1/cos(lat)). Voil