Georeferenced images on Garmin!!

[GraemeWi]

http://garmin.blogs.com/softwareupdates ... steps.html

Yet to have a play with this myself

[kiwitonita]

This looks like a very interesting development Garmin Beta: Custom Raster Map Support for Oregon, Colorado and Dakota

[rediguana]

Just saw this on GPSFix - very cool indeed! How to get the LINZ geotiffs in there is the next question

Bugger - it only supports up to 100 images of around 1024x1024 pixels... still I'm sure there will be some fun experiments creating maps. If anyone creates one and wants to share - feel free to post them in this thread.

[radionut50]

Yes - looks like fun.. but I don't like the "..and calibrate your image with google earth.."... that will give you a map that shows you around 20meters to the left of where you actually are, around Hamilton anyhow.

We would need to devise a method of referencing the image more accurately in this part of the world.

[rediguana]

edit by rediguana: moved the georeferencing posts into a single thread

Yes - looks like fun.. but I don't like the "..and calibrate your image with google earth.."... that will give you a map that shows you around 20meters to the left of where you actually are, around Hamilton anyhow. We would need to devise a method of referencing the image more accurately in this part of the world.

Well, I'm wondering how it will work with geotiffs (e.g. images that are already georeferenced). If the custom maps are just a combination of KML and JPG tiles (I haven't looked at this yet). It should be possible to batch produce 1024^2 georeferenced tiles of say the LINZ Topo50 from the source geotiffs. A lot of data and number crunching.

It may also be possible to do some basic crunching with something like QGIS in combination with road shapefiles. The real question is going to be how well the free Google Earth handles already georeferenced files. Wish I had time to play with this.

[rediguana]

I've just posted a feature request to ask for geotiff support.

[GraemeWi]

I've done a quick trial - it's really hard to get the LINZ geotiff to align with Google Earth, it really shows quite a few integrity issues between the geotiffs and Google.

I converted a small segment of a tiff into a jpg, loaded into GE, fiddled for ages to try and get everything to align, did the export etc and fired up the GPS

First thing that threw me was the GPS being set to Track Up and the map on it being upside down - fixed that

Map looks sexy on the GPS screen

Not too sure I would want to navigate using it! After using vector maps rasters are ummm, interesting

Much more experimentation required!

http://www.gwprojects.org/public/Henderson.kmz

[rediguana]

it really shows quite a few integrity issues between the geotiffs and Google.

I suspect that the only real problem is the model that Google Earth uses - some of the newer imagery appears to much more accurately georeferenced than the old..

I've just posted on the NZ Open GIS list to see if there is a way of scripting geotiff in 1024x1024 tiles, convert to JPG, and have a script use the geotiff info to produce the KMZ data automatically - e.g. leave Google Earth out of the whole process.

This is also the reason I've asked for geotiff support - so much easier just to load the geotiff as it is already georeferenced.

[rediguana]

OK, so it looks like we might be able to do this - from some googling and thinking.

1. Use gdalwarp to convert from NZTM (EPSG:2193) to WGS84 (EPSG:4326) and produce tiles
2. Use gdalwarp to convert tiles from TIF to JPG and produce JPG world file
3. Read JPG world file and create doc.kml for each image

This thread on the ExpertGPS forums has some interesting information that is likely to prove useful as well

[rediguana]

Just been made aware of MapTiler - might make making custom maps quick easy if it does the full job...

Also found this script here which shows some promise.

[GraemeWi]

Having fun and mucking around - grab a screenshot from GE, load it back in and reference...

Below images are GE with everything switched off except the view, and overlayed on the GPS with the normal NZOGPS street maps and POI on screen





Had another idea for an application - a blank white map with a 'follow the dotted line' type path on it which leads the user to something

[rediguana]

Below images are GE...

Nice.

Had another idea for an application - a blank white map with a 'follow the dotted line' type path on it which leads the user to something

That something is known as a puzzle cache

[rediguana]

I've also made a request to the guy that produces MapTiler to add the Garmin Custom Map export capability - it might be useful if a couple of people go to this page and sign up, and vote for the feature I've added asking for Garmin Custom Map export!

Anything to avoid using Google Earth for georeferencing...

[rediguana]

GPSFix has a good summary up as well now. Seems like there is a lot happening in terms of advocacy to get software tools to support GCM

http://www.gpsfix.net/garmin-custom-map ... dom-stuff/

[rediguana]

Whilst waiting for the Indonesian maps to download, here is another page of interest. Hamish has written a script to produce tiles for GPSDrive.