DonK

How to merge jpeg maps?

6 posts in this topic

I regularly need to merge several map tiles where each tile is a separate jpeg file. I then import them into EGPS as a single, scanned jpeg file. I have been using Photoshop to open the individual files and align and merge the map tiles into a single file.

Does anyone have different, perhaps simpler way of doing this merging?

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Are they all the same size, and do they align perfectly if you simply place them side-by-side? Or does there need to be some manual intervention or image recognition to overlap them properly?

Can you get them as 256x256 tiles in a web Mercator projection?

 

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These are historic USGS 7.5 minute topo maps from the U. of New Hampshire . Some indicate they are polyconic projections. Each paper map has been scanned in four, 1700px x 2800px  sections, and each section saved as a jpeg file.  So they align perfectly when placed side-by-side.   If I use more than one, four section map, then I remove the collars. 

These maps also are available for download from the USGS in several formats, including geotif  and they are a single file containing the whole map, not four sections in four files. The collars would have to be removed and if more than one map needed to be used, they would have to be merged somehow. I'm not aware that EGPS can load more than one scanned map file at a time.

 

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The Automatically Add USGS Topo Map command in the latest version of ExpertGPS should allow you to download many of the historical topos. I left out the really old ones, but if you need them, you can download them through this interface:

https://ngmdb.usgs.gov/maps/TopoView/

 

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That USGS site is the site I was referring to. If I download the tif version, there are four files per map - geo.tfw, geo.tif, geo.tif.prj and geo.tif.xml. Where do I save them in EGPS in order to access them with the  Automatically Add USGS Topo Map command?

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Click Add and Calibrate a New Scanned Map, and select the .tif file. If the .tfw file is in the same directory as the .tif, ExpertGPS will do most of the calibration for you.

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