I continue my quest to become an expert KMZ file maker...but with all the IMG map creation expertise around here, I feel like becoming an expert at KMZ files is kind of like hanging out at a party of math PhD's and saying "yeah, but I'm REALLY GOOD at addition!"
1) workaround for Google Maps limitation on 3 Mb KMZ files
: Since we (those of us creating KMZ files for Garmin GPSr) already have to use some kind of tool (I use MAPC2MAPC) to accommodate the Garmin limit of 1 Mb, we are halfway to the solution:
a) after creating the multiple tile KMZ file for the Garmin KMZ, create multiple smaller KMZ files with the right number of tiles to keep each KMZ file less than 3 Mb. (I have found that the best performance is actually with KMZ files less than 1.5 Mb). This is really easy to do if you have one KML file (from within your 'master' KMZ) that references all the tiles. You just use that KML as the basis for all of the KML files in the smaller KMZ files - just delete the references to the tiles not being used in each KML file associated with the multiple smaller KMZ files. Essentially you're building the multiple smaller KMZ files with a text editor to manually edit the KML files, and manually compiling the smaller KMZ files with a ZIP file editor.
b) Create a KML file with "network link" attributes that can be read by Google Maps.
This is all easier to understand with an example. See my "Middlesex Fells" KMZ here:http://www.gpsfiledepot.com/maps/view/579/
The KML that is used to generate the Google Maps 'preview' is here:http://www.dbperry.net/maps/fells.kml
You can download it and open it up in a text editor to inspect the syntax. Basically it is calling 10 separate KMZ files which 'tile' together to create the full map.
Unfortunately, the Google server 'reading' / 'loading' of KMZ files seems slightly unstable - sometimes you have to 'refresh' your browser a few times before all the tiles will load in.
2) The same "network link" attribute in a KML file can be used to display overlapping KMZ files
. See this example:https://maps.google.com/maps?f=q&hl=en&q=http://www.dbperry.net/maps/nw_fram.kml
(which are the maps in my Northwest Framingham "Bay Circuit "E to K" KMZ Series:" http://www.gpsfiledepot.com/maps/view/607/
It even uses the draw priority of each KMZ to display the KMZ files in the correct / intended overlap!
3) There is a workaround to simulate transparency for KMZ maps in Google Maps
. KMZ files support the GIF file format, and the GIF file format supports transparency. So you can:
a) convert your JPEG map to a GIF
b) replace the 'background' color of the GIF with 'transparent' pixels. Photoshop Elements or Photoshop can do this.
c) Create a KMZ file with the GIF file as the image.
d) When you load that KMZ file into Google Maps, it is "semi-transparent"
I tried this and it is pretty cool, but I didn't save my example, because...
I have abandoned this approach because Garmin does NOT support KMZ files made with GIF files. Garmin only supports JPEG. So I am going to focus my efforts on KMZ files that are compatible with the Garmin GPSr, which is my real reason for creating KMZ files. Too much extra work just to get transparency in Google Maps (although it does make the Google Maps KMZ implementation much more usable).
4) Finally, last, but certainly not least, I found the Gmap4 website
, which (among other things) uses the Google Maps API to display KMZ files on all kinds of maps. For example:http://www.mappingsupport.com/p/gmap4.php?q=http://www.dbperry.net/maps/nw_fram.kml
Notice the menu in the upper right corner - you can choose 13 different 'foundation' maps as the background!
Lots of neat features on the Gmap4 website: http://www.mappingsupport.com/p/gmap4.html
My next project will be to create an interactive, hot-linkable Gmap4 map with all of my KMZ maps. In other words, a big (small scale) view of New England with all of my KMZ maps displayed. Clicking on each KMZ map will bring you to the correct GPSFileDepot page where you will be able to download the Garmin compatible KMZ.