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I want to download an appropriate aerial image. Since they are huge, disk-space consuming, and time-consuming to download, I want to zero in on the right one. The directory lists images for my area (UTM zone 10 -- San Francisco and Oakland and beyond) named like this, in this order:

10SEG355985.tif
10SEG370880.tif
10SEG370895.tif
10SEG370910.tif

Can't find helpful metadata. Is the "37" degrees of north latitude? That would make sense. But what is the "0985" part? And the "SEG" part -- that is a UTM convention, correct?

The website is "Cal-Atlas Geospatial Clearinghouse" -- http://www.atlas.ca.gov/download.html#/casil/imageryBaseMapsLandCover/imagery/urban_imagery/0.3meter_urban_area/overflights/san_francisco_oakland

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    the "0895" part could be decimal minutes (without the decimal point) – Ian Apr 16 '12 at 5:18
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It is always worth opening a file in your GIS or checking to see if it has a world file etc before assuming there is no metadata whatsoever.

These files are geoTiffs. If you open one in your GIS you will find relevant metadata embedded. Opening 10SEG325910 tells me that it is a 8-bit unsigned integer raster in UTM zone 10 with an origin @ 532500, 4191000 and pixel sizes of 0.3,-0.3 (i.e. origin is top left).

From this I conclude that the naming convention is to take the last five digits or the x and y origin coordinates and divide by 100.

  • Thanks. It worked out for me, after some floundering. (Had to convert my lat-lon to UTM10, and also had to realize that the northing of the desired tile is bigger/higher than my position's northing.) – Catlike Apr 19 '12 at 7:01
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You might also consider downloading the index shapefiles, loading them into your GIS along with a streets layer or basemap and figuring out which tiles you need to download.

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