aerial photographyarcgis-10.0google mapsmerge
I want to have a high resolution aerial photo of a catchment area. I took some images from google maps and georeferenzed these and saved them as a layer file. but how can I merge them now that I have one image for the whole catchment area?
The merge tool didn't work. The images are .png s.
I'm sorry, I'm new to ArcGIS and I couldn't find an answer in the web. Also a mosaic layer doesn't seem what I want…
Thanks for your help!
MapQuest Open Aerial Tiles
Global Coverage (higher zoom level in the US)
MapQuest Open Aerial Tile URL example:
Terms of Use
The MapQuest Open Tiles are available for use for free under the following conditions: http://developer.mapquest.com/web/products/open/map#terms
MapQuest Open Aerial Tile URL example: http://oatile1.mqcdn.com/tiles/1.0.0/sat/15/5240/12661.jpg
Replace http://a.tile.openstreetmap.org with http://oatile1.mqcdn.com/tiles/1.0.0/sat.
Note: There are 4 subdomains set up for the MapQuest-hosted tiles: oatile1 to oatile4. All subdomains point to the same CDN. Just like with OSM’s a.tile to c.tile subdomains, the MapQuest subdomains are provided to work around browser limitations on the number of simultaneous HTTP connections to each “host”. Browser-based applications can request multiple map tiles from multiple subdomains faster than requesting map tiles from just one subdomain.
Please also note that global coverage is provided at zoom levels 0-11. Zoom Levels 12+ are provided only in the United States (lower 48).
Answering my own question: Those black pixels in the images represent a "NoData" value. If I tell the gdal merge code that pixels with a color value of 0 are "NoData," it can correctly stitch the images together. (The "NoData" value isn't necessarily set to 0, it can be any value not otherwise used in the image, but in the case of NAIP ortho images, it was 0.)
The gdal_merge.py program accepts an optional -n argument to set the nodata color value, however I had a problem using that on my system. Apparently, setting the -n option causes the Python code to go through a branch that tries to import a package that I was missing.
Rather than fiddle with the missing package, I chose to merge my four GeoTIFF image files using the gdalwarp tool. I passed the same coordinate system for both source and target, since I just wanted to merge, not warp. I specified the nodata value of 0 by passing the arguments -srcnodata 0 -dstnodata 0.
Best Answer
The Mosaic to new raster function is what you need. Don't add an extension for the output raster, which would make it an ESRI GRID, which can be clipped as you like.