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leszekp
USA
2 Posts |
 Posted - 15/02/2010 : 20:22:30
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Stumbled across this forum while searching for posts on G-Raster and Moagu. As the author of both of those software programs (quick shout-out to Allan, one of the first users of Moagu), and owner/reviewer of several GPS units, I thought I'd add a few comments.
1. G-Raster does indeed create KMZ overlay files out of raster imagery for the newer lines of Garmin GPS units (Colorado/Oregon/Dakota). But while it will accept a KMZ overlay file as input, it will also convert georeferenced imagery like GeoTiffs and MRSID into a Garmin-compatible KMZ overlay, as long as the coordinate system is supported by the GDAL. Unlike images calibrated in Google Earth, these should be absolutely accurate to within a pixel or two of the actual cordinates. Positions in Google Earth can be way off, as much as 100 meters; in my area, they're about 10 meters off. So if you use Google Earth to calibrate your raster imagery, GIGO.
Garmin units require that each image tile be no more than 1024 x 1024 pixels in size, and that you have no more than 100 tiles loaded into your unit; G-Raster can chop up and resize an image to meet these requirements. It can also handle raster imagery with worldfiles, if you know what the EPSG code for your coordinate system is. And it's completely free for processing georeferenced raster imagery. Find it here:
http://moagu.com/?page_id=155
2. I have one of the Garmin Oregon 450t units for review for my website, http://freegeographytools.com; this is their latest model, and sports an "improved screen visibility" compared to earlier units . Still working on the review; while there's much to like about this unit, several of Allan's points are fully justified. The color screen is gorgeous, and screen visibility in sunlight is usable, but clearly inferior to the 60Cx series. And there's only one button, for power and backlight; everything else has to be done through the touch interface. The Oregon touch interface needs some major work; it can take multiple steps to do what could be done with a single button push on the 60Cx. For example, if you're on the map screen and want to mark a waypoint, you have to exit the map screen, press the Waypoint icon, then press the Create Waypoint icon. But it's much faster to do data entry with a touch screen instead of a rocker switch, so that's an improvement. Finally, after touching the screen for a few minutes, it becomes so soiled with fingerprints that daylight visibility is further degraded; fortunately, it will work with a stylus.
It's great that Garmin has added the ability to import your own raster maps for free (unlike deLorme, where you have to pay $200 for xMap to do that with their PN series of GPS units). But raster map management still needs work. You can only have a maximum of 100 total map tiles loaded in the unit, each with a maximum size of 1024 x 1024 pixels, so the total area you can cover is limited. And you can't turn individual overlays on and off; for example, if you have a topo map for an area, you can't turn it off and turn on an aerial view of the same area. I have to believe this will be fixed eventually.
I actually like this unit a lot, and will be sorry to send it back. But the touch interface needs improvement to be a good GPS unit for field work.
3. In addition to the deLorme units mentioned by Allan, the Magellan Triton series of GPS units can display georeferenced raster imagery. Here's a link to my review:
http://freegeographytools.com/2009/a-review-of-the-magellan-triton-2000-gps-receiver-part-ii-out-in-the-field
The Triton has buttons, and the 1500/2000 models have a touch screen as well. Raster map imagery can be generated using the free programs TritonRMP Maker, TritonRMP Helper, and Mobile Atlas Creator:
http://freegeographytools.com/2009/create-custom-raster-maps-for-the-magellan-triton-gps-units-with-tritonrmp-maker
http://freegeographytools.com/2009/tritonrmp-helper-upgraded-to-version-2-0
http://freegeographytools.com/2010/raster-maps-for-garmin-and-magellan-gps-units-and-mobile-phone-apps-with-mobile-atlas-creator
Mobile Atlas Creator can also generate KMZ files for compatible Garmin units.
You can load as many raster maps into the Triton unit as the max. 16 GB SD card can handle, and turn them on and off. And the combination of buttons and touch screen for 1500/2000 units is a good mix of usability and flexibility. But screen visibility is very poor in sunlight conditions with the backlight off, and mediocre with the backlight on. Shade it with your body and the screen view is acceptable, but using the backlight really drains the batteries.
4. If your maps are graphic maps, with well-defined blocks of color, another option with Garmin units is to vectorize them and convert them into Garmin's vector format. Mapwel (http://mapwel.biz) can do this, in addition to its other functionality as a Garmin vector map editor. Moagu (http://moagu.com) has a front-end to the free utility bmap2MP, which can also create vectorized maps. Moagu can also generate full-color raster maps for some Garmin handheld GPS units (60Cx, 76Cx, some eTrex models); as Allan said, it's a bit of a hack, and display draw speeds range from very slow to abysmally slow. Vectorized maps will work on any Garmin unit, and are generally faster to draw than raster maps. On the downside, vectorized maps aren't a good choice for maps with lots of fine detail, or aerial imagery, as the vectorization process and limits on the numbers of colors can cause substantial loss in raster imagery detail. Moagu's raster maps work better for that, but are slow to display and redraw.
I personally own the Garmin 60Cx and Triton 2000. For raster map display, the Triton often proves useful, and the Garmin Oregon wouldn't be a bad substitute for that. But for general field work, accuracy, ruggedness, reliability, etc., the 60Cx is hard to beat; they'll have to pry it out of my cold, dead hands. Use a program like MapWel, GPSMapEdit (http://www.geopainting.com/en/) or Moagu to convert your GIS data into a 60Cx-compatible format, and you can get much of the functionality you're looking for. |
Edited by - leszekp on 16/02/2010 18:38:58 |
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ewanduffy
Ireland
3 Posts |
Posted - 05/03/2010 : 22:25:17
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I was going to ask the same question about ability to upload self created maps as my GPS unit was stolen last night (was in my brother's car - he was taking it around Ireland with him to track the main roads for me).
It looks like I should go for the Garmin 60Cx. The plan is to upload vectors of the roads I have already tracked - useful when I visit an area to spot fill. Am I right in thinking that with the software options mentioned in previous posts, I can do this with the Garmin 60Cx? Topography is not of interest to me (will be looking at roads, railways and canals principally). |
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leszekp
USA
2 Posts |
Posted - 17/03/2010 : 23:48:10
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| Yes - you can convert vector data to a 60Cx-compatible format. |
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Mapmaker maps in hand held GPS
