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Author Topic: Loading IMG files with no TBD or TXT file  (Read 3935 times)

jgaffney

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Loading IMG files with no TBD or TXT file
« on: January 19, 2011, 12:11:30 PM »
I've been reading the tutorials and discussions here about loading custom maps on my GPS and I'm very excited about the possibilities. I downloaded the California topo file and loaded a portion of it on my eTrex Vista Hcx, and I am underwhelmed by the lack of detail on the map. I was hoping for a richer image, similar to what I have in TOPO!

I am planning a hiking trip to France for this fall, so I have been researching downloadable maps for the French Alps. IGN has the best 1:25,000 maps, and they even have a software program comparable to TOPO!. But, it won't transfer images, only points and tracks. I found a program at SourceForge called TopoMap, which downloads img tiles from IGN, or the equivalent servers in Spain and Germany.

In reading the tutorials here for installing img files in MapSource, the section for those of us with img tiles but no tbd file, the author references a txt file as a stand-in for the tbd file. I couldn't find any reference for what this txt file contains, or how to create one. I'm anticipating having upwards of 1,000 img files to compile, with no way to arrange them.

Any help here?

Boyd

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Re: Loading IMG files with no TBD or TXT file
« Reply #1 on: January 19, 2011, 12:16:58 PM »
Those won't do you any good with Mapsource or a Garmin GPS. They appear to be raster image tiles - pictures in other words. This is something completely different from Garmin .img files, which are vector based maps in Garmin's proprietary format.

maps4gps

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Re: Loading IMG files with no TBD or TXT file
« Reply #2 on: January 19, 2011, 12:45:24 PM »
The CA topo was a one-time effort by a non-gpsfiledepot person for a specific purpose different than what mapsets here are usually made for.  It is overcontoured and did not use POI's from USGS's GNIS files.  What details did you find lacking?


Boyd

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Re: Loading IMG files with no TBD or TXT file
« Reply #3 on: January 19, 2011, 01:03:31 PM »
I am underwhelmed by the lack of detail on the map. I was hoping for a richer image, similar to what I have in TOPO!

Do you mean National Geographic TOPO! Those maps are scans of USGS maps that are enhanced with hill shading. You are just never going to get anything remotely resembling that on an eTrex. Your gps will only use maps created in Garmin's proprietary format. The National Geo maps are what we call "raster imagery" which are basically pictures - they were created by scanning paper maps.

Some of the newer Garmin models support this kind of map, but the eTrex series does not. Even the new models are limited in that you cannot cover a very large area with raster imagery (about 25 miles x 25 miles from my experience).

Garmin's format is vector based, meaning that the map file is just a database of coordinates with instructions for how to connect them on the GPS screen. So it's basically "connect the dots" to create lines (such as roads), polygons (such as lakes) and points (such as cities). Vector based maps have their own advantages, but they never look like raster imagery.

jgaffney

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Re: Loading IMG files with no TBD or TXT file
« Reply #4 on: January 20, 2011, 09:31:35 AM »
Do you mean National Geographic TOPO! Those maps are scans of USGS maps that are enhanced with hill shading. You are just never going to get anything remotely resembling that on an eTrex. Your gps will only use maps created in Garmin's proprietary format. The National Geo maps are what we call "raster imagery" which are basically pictures - they were created by scanning paper maps.

I understand that part. The TOPO! maps are georeferenced raster images, so I am putting my cursor on a picture, but the software knows where it is in the world.

Quote
Some of the newer Garmin models support this kind of map, but the eTrex series does not. Even the new models are limited in that you cannot cover a very large area with raster imagery (about 25 miles x 25 miles from my experience).
25 miles by 25 miles is plenty of coverage for me. My usual 3-4 day backpacking trip would be contained in an area like that.

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Garmin's format is vector based, meaning that the map file is just a database of coordinates with instructions for how to connect them on the GPS screen. So it's basically "connect the dots" to create lines (such as roads), polygons (such as lakes) and points (such as cities). Vector based maps have their own advantages, but they never look like raster imagery.
What about the software that I've seen, here or somewhere, that "vectorizes" a raster image?

Boyd

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Re: Loading IMG files with no TBD or TXT file
« Reply #5 on: January 20, 2011, 09:46:32 AM »
There's MOAGU and Mapwel:

http://moagu.com/
http://mapwel.eu/

You can try the free demo's and see what you think. Personally, I feel you'd be trying to fit a square peg in a round hole though. The Garmin units that have native support for raster imagery are the Oregon, Dakota, GPSMap 62 and GPSMap 78 series. There are a variety of tools for making these maps, both free and commercial. For simple projects, you can just use Google Earth: http://www.garmin.com/garmin/cms/site/us/onthetrail/custommaps

The file format is .jpg files incapsulated inside a .kmz container. There are some strict limits to what you can do however. Each .jpg can be no larger than 1024x1024 and you can only have a maximum of 100 .jpg's. I've posted a number of examples here - you could use Google Earth to view them: http://www.gpsfiledepot.com/maps/byuser/282/