I was a park ranger for about seven years, and I loved being a park ranger, but I didn’t like working with the park service. So I left, got my master’s degree in geography and started making maps. They say write what you know about if you want to be a writer. Well, I mapped what I knew about. So I started mapping parks, and one thing led to another.

Lam: What is your process for making a map?

Harrison: The first thing is just to look and see how many people are going to an area, so you find the popular places. I find out which places people are interested in going, and I drive around to all the campgrounds and trailheads and look at the license plates to see where they’re coming from and if there’s a market to sell the maps.

Making a map is like any other kind of project you can think of—painting a house, making a quilt, preparing a big fancy dinner for friends. There’s a lot of work and research that goes into it. You have to look and say: How much has already been done, and do I have to do it all over myself? Is there information out there that I can get for free, or pay for?

A lot of research is looking into where the data is coming from, because maps are very information-rich graphics. There’s roads, and trails, and lakes, and elevations, campgrounds, all those squiggly lines we call contour lines on elevation. And the question is: How do you find that information and how do you make it all fit together? So there’s a huge amount of research into the best and easiest way to get that data, and how to make it all come together. And that's a tremendous amount of work.

Lam: How long does it take to make the map once you decided on a location?

Harrison: Usually about two years. Things have gotten a little easier over the years. I used to go out and hike every trail. I’ve done a lot of trail hiking with a measuring wheel and a GPS unit. There are some places in this country where the maps are quite old, and some of them don’t have the trails on them that the parks have. They don’t have the boundaries. And finding that information is really time consuming.

Over the years, I’ve figured out various ways of finding that data and double-checking that data. I don't have to go quite as often as I used to. You’ve got the field work, you’ve got the research, then you’ve got the compilation—bringing it all together.

Lam: Has your mapmaking process changed since you started in the 1970s?

Harrison: Oh yeah. It changes about every 6 months. I figure out what I hope is a newer, easier, faster way of doing things.

One major thing I’ve changed in the last couple of years is using information that’s available from the different park and forest agencies. Those agencies use something called GIS, which means Geographic Information System. And it’s basically like a database of all the features in an area, and this information is attached to actual lines you see on a computer screen.