Creating Custom Map With Transparent Polygons

[johnnyslickster]

I'd like to create a custom map of bedrock geology that could be overlaid on topo maps and Birdseye imagery and show the labels for each bedrock area, just like the PLSS map available here has a label for each section.  I have the data as a shapefile, which is publicly available.  I've used GPSMapEdit to convert polygons to lines, and to create solid polygons that cover up the other maps loaded in the GPS, but I can't figure out how to create transparent polygons to go with the boundary lines.  Just converting to lines isn't sufficient because all the  bedrock areas are contiguous- while the boundary lines can be labeled, it's not clear which side of the boundary the label applies to.  I've tried reading up on custom typ files, but I'm a little baffled regarding how to actually create and use a transparent polygon type.  I have a Garmin 62, so it's easier to just copy a completed img file to the GPS rather than using Mapsource or Basecamp to send it.  Any help would be greatly appreciated!

[Boyd]

"transparent" is really a bit of a misnomer. Normally polygons would be covered with 32x32 bitmap images that can contain two colors. But you can use transparency as one of the colors, then make a pattern of dots with the other color. So you end up overlaying a dot (dither) pattern on objects that have a lower draw order.

I think the easiest way to create custom types is to use the online editor here: http://ati.land.cz/gps/typdecomp/editor.cgi. This will let you edit the bitmaps graphically. Be sure to choose the correct drawing order for the polygon so it is not covered by other polygons in the map.

The nice thing is that you work directly with the binary .typ files and don't need to mess with a text editor or cgpsmapper. Recently someone here pointed out a new standalone utility for custom types that also looks very nice: http://pinns.co.uk/osm/ostyp.html

[Seldom]

Can you find your geological information as a raster?  I've loaded raster geological quads onto my 62 as Garmin "Custom Maps".  No need to mess with TYP files then.

[Boyd]

Only problem is that he says he wants to overlay this info on Birdseye imagery. You can't do that with a raster image...

[Seldom]

True, he'd have to rely on vector graphics for the rest of the map, but graphics on the USGS geology maps are probably clearer than anything he could come up with. 

Do you have any examples he could use for partially transparent polygons?  The wooded areas on Desert Southwest are semi-transparent and overlay all sorts of other polygons, but its a big download.

[maps4gps]

For the PLSS mapset, I created polygon type 0x21 with a color of 'none' and used cgpsmapper to build the .typ file from a .txt file.
What area are you interested in, and what is the source and scale of the geological data?

[Boyd]

If you only define a color of "none" in a polygon, it will be invisible, not transparent! This can be useful I suppose if you would like to click on a part of the map and display the string associated with the type but not see a polygon.

To create "transparent" polygons, just use the online editor I linked to above. Click on the first tab "Create" then "Create a completely new TYP file" and finally "Add new polygon". Now decide what polygons you want to use (this will completely depend on your map and what you want to do). Choose a drawing order from the dropdown that is higher than the other polygons in your map.

Now choose a color mode from the dropdown. To keep it simple for a test, choose 14 day+night 1-color transparent bitmap. Now create whatever pattern you like by clicking in the grid with the foreground color - the background "color" will be transparent.

For a quick test, choose the dropdowns to repeat the pattern every 4 pixels on both x and y axis. Click once in the top left corner of the grid and notice how it repeats. If you click the refresh button, it will show a preview of the pattern over different color backgrounds. You can then try changing the color, dot pattern, etc.

When done, click the save button, scroll down to the bottom of the page and click Download TYP file. You can now test this with your mapset.

[jbensman]

If this is for non commerical use, feel free to downland and install either my Eastern or Western Landownership maps.  They are both transparent polygons.  Instead of trying to figure out how to create the typ file (or if you want to see an example of how it is done), use the typ file for either of these maps.  You can open it at http://ati.land.cz/gps/typdecomp/editor.cgi and see which poligons have a custom style assigned to them and see what color they are using.  Just change your polygons to the polygon you want.

[maps4gps]

If you only define a color of "none" in a polygon, it will be invisible, not transparent! This can be useful I suppose if you would like to click on a part of the map and display the string associated with the type but not see a polygon.

It work fine (and as intended) in my PLSS and QQS mapsets (and also in geological and soil maps).
These are contiguous polygons with a line(s) created to seperate the polygons.  The label shows as intended within a polygon.