Gtopo Tutorial
OK, you have built gtopo, loaded up your map archive, and now you want to look at some maps.
The gtopo in on some directory that is on your search path.
Type gtopo to start the program. A rectangular window should open up and show you
something. If it is all white, this is probably because the starting latitude and longitude
are set for Flagstaff, Arizona and it cannot find any maps in your archive for that location.
Setting up a config file
Create a directory .gtopo in your home directory and then use an editor to create a
file config with contents as follows:
# Near Las Vegas Nevada
starting_lat 36.2338
starting_long -114.9894
Set a latitude and longitude of some spot you expect gtopo to be able to find
in your map archive and restart gtopo. This settings file can be used to customize
gtopo (in lieu of hacking things in the code and recompiling).
Manipulating the map
One of the design goals of gtopo is to present you with an uncluttered window
with nothing but a map. There is no menu, and not even a menu bar.
You can do virtually everything you want to do with gtopo using just a mouse
(especially if it is a wheel mouse). Alternately you can use the keyboard,
but keyboard manipulation was provided primarily to make me happy when I am
using my laptop which has a horrid touch pad.
A little fiddling around with the program and the following instructions
and hopefully you will find this a simple to use interface.
Changing scale
With a wheel equiped mouse, just use the wheel.
With a disfunctional mouse (or if you prefer),
use the page-up and page-down keys on the keyboard.
Page down zooms in, and Page up zooms out.
(Unless you are on OS-X, which has serious brain damage with respect
to the page up and page down keys -- see my notes on running
gtopo on OSX for tips on this issue.)
Zooming in this fashion does not rescale the current map image, but
changes the map series. The NGS map sets ship with 5 different scales of
maps as follows:
- Series 1 -- "State" - shows the entire state on one screen.
- Series 2 -- "Atlas" - a good road atlas for paved highways.
- Series 3 -- 1:500,000 - a not very good road atlas, with topography.
- Series 4 -- 1:100,000 - nice topography, similar to the AMS 125K maps.
- Series 5 -- 1:24,000 - superb, the digitized 7.5 minute maps.
Moving around
Notice that there is a tiny blinking "plus" sign marking the center
of the viewed region, this is the all important center point.
The usual way to move around, is to use the left mouse button.
Push and hold the left mouse button and move the mouse to drag the map.
The right mouse button when clicked will move the current mouse location
to the center of the viewing region.
The four keyboard arrow keys move up, down, left, and right.
Note that the "up" key does not move the map up, it moves your position
on the map up. The map actually moves down.
Printing
To print a map, I have found that the default window of 640 by 800 prints
nicely on a 8.5 by 11 inch sheet of paper (on my printer anyway). With the mouse
anywhere on the map, hit Control-S and a file gtopo.jpg will be
created in the current directory. This is a JPEG image of the map you
were just viewing, and it can be fiddled with via the gimp, inserted into web
pages or fiddled with using whatever image manipulation tool you choose.
What I do to print maps is to conver the JPEG file to postscript using
image magic (since I have a postscript printer) as follows:
convert gtopo.jpg map.ps
lpr map.ps
That should get you going until I add more features and/or write a reference manual.
Feedback? Questions?
Drop me a line!
Gtopo / tom@mmto.org