Monday, December 3, 2012

Garmin Custom Maps

Newer Garmin GPSs (including the 62, Oregon, Colorado and Montana series) allow you to use KMZ (Google Earth) files as custom map layers.  You can now export CalTopo's map layers and use them with these devices.

  1. Go to or click Print and then choose KMZ.
  2. Navigate to the area you want to export
  3. Set the map background using the dropdown at the top right.  You can combine layers as usual, e.g. shaded relief + topo + slope shading
  4. If needed, click "fit selection to screen" and drag the rectangle to cover the area you want to export
  5. Choose a zoom level, remembering that you can only fit 100 images total on the GPS
  6. Click "Download KMZ", or click "Connect to GPS" to send the file directly to a newer Garmin GPS using the Communicator plugin.

Exporting avalanche slope shading to a KMZ file.
To load a KMZ file into your GPS (if you didn't transfer it directly using the plugin):

  1. Plug in your GPS using USB.  It should show up as a removeable drive, just like a USB thumb drive
  2. Create a \Garmin\CustomMaps\ directory on the GPS, if it doesn't already exist
  3. Copy the .kmz file into \Garmin\CustomMaps\
You may also have to turn on the Custom Maps layer on your GPS.

Nationwide Google Earth Coverage

I've supplemented the existing KML export capability with a new feature that dynamically generates KML files as you fly around in Google Earth.  This means that you can get nationwide coverage from a single KML file, without needing export small areas on a one-off basis.

Try it!

Click here for USGS Topo maps
Click here for USFS Road and Trail maps

Forest Service maps on top of USGS topos, with large-scale coverage.

Please note that this will become a paid feature in early 2013, but is free for now while I finish development.

Printable PDFs

CalTopo has always allowed you to print maps directly from your web browser.  That feature isn't going away, but it has some disadvantages:

  1. Poor Browser Support.  You can make nice prints with Chrome, but Firefox doesn't respect CSS print margins and if you're not careful the map can easily bleed over into a second page.  IE prints the URL and title at the top of the page, with no way for the user to turn them off.
  2. Low Resolution.  On my computer at least, setting the map size in inches gives you a print resolution of only 100ppi.
  3. Fixed Scales.  There are a limited number of zoom levels available, and the scale doubles with each one.  Often zoom 14 is too broad and 15 is too narrow; there's also no way to print a 1:24K map.
In response to these issues, CalTopo now offers server-side PDF generation.  Pick your layers, draw a rectangle on the screen, and hit print.  You'll get back a high resolution PDF that will print exactly as it looks, no muss, no fuss.

At this time, PDF generation can only be used to print CalTopo's base layers.  It can't be used to print Google's layers or maps from other sources.  It also won't show waypoints and tracks from saved maps, although I hope to add this at some point in the near future.

Try it by going to, or by clicking on the "printable PDFs" link inside the standard map page's print mode.  Please note that this will become a paid feature in early 2013, but is free for now while I finish development.