Blog Archives

5/2/07 Team trials

This weekend is the qualifier for the US Team going to World Orienteering Championships (WOC). I'm excited about going. While I don't have a chance of making the team, I feel like I'm actually pushing the top guys a bit rather than just filling out the field. Of course, that would be a lot more true if the venue was some nice open ridge and valley terrain. Instead, it's the glacial moraine of southern Michigan. I suck at that stuff. Still, should be fun.

5/3/07 Strategy for this weekend

In a nutshell, don't get lost. I've made some whopping mistakes on glacial terrain in the past. On the other hand, I'm not going to beat anybody walking. It would be nice to have a few days to adjust to the terrain. But, I don't, so I'll have to find a way to transfer the ridge and valley skills I have.

My plan is to try to find relatively safe routes following linear features. Of course, the course setters have no doubt done their best to negate that by setting legs that don't have good safe routes. Still, given my track record on this stuff, I think I'm better off adding some distance and keeping my errors in check. We'll see how it goes.

5/6/07 1-1-1

Let's call it even. The sprint at Team Trials was a disappointment. I just didn't have the legs to turn in a good time. The middle distance race on Saturday was perhaps my best run ever on Blue. Today's long event performance was about what I would expect given the terrain. I finished OK with only one really bad mistake and a few legs run quite well.

Going into the event I figured a top-10 overall placing would be a good result. The top 4 or 5 go to World Orienteering Champs, but I knew I wouldn't make that cut. That's pretty much how it shook out. I didn't get my final position, but I think it was between 10th and 12th.

Despite the mixed result, I'm coming away from the weekend feeling pretty good about the meet. True, it could have been a bit better, but it could have been much, much worse. Being disciplined about taking safe routes and not overrunning my navigation kept the disasters at bay (except for one nasty 8-minute error today). One bad boom in 53 legs on unfamiliar terrain is an error rate I can live with.

Now I'm left with two questions to answer: how do I get to where Saturday's result is normal for me rather than outstanding and how do I push my best results up another notch? Not sure on either right now, but with my best spring season wrapped up, I think I'll take some time to enjoy the fact that I'm as good as I've ever been and wait until fall to stress over improvement..

5/7/07 Green menace

The most commonly heard complaint after Sunday's race was that the vegetation was thicker than mapped. The race organizers were apologizing for it prior to the start. Even the competitors from "tough guy" regions like Kansas and Texas commented on it. For some reason, it didn't bother me in the least.

I can only attribute this to the HTFU workouts I've been doing. It's not that I don't feel thorns; I'm just getting used to them. I've gotten to the point where I think that nasty vegetation works in my favor. Sure, it slows me down, but it slows down other people more. More importantly, it doesn't piss me off. Getting mad at the conditions is a sure way to screw up - you have to stay focused on the things in your control.

I remember reading an interview with Laurent Fignon where he commented on how he liked the fact that the Tour de France was so much harder than the Giro d'Italia. His quote was, "I've never won the Giro by 15 minutes." His point was that adverse conditions help separate out the field. The tougher the race, the less chance of an "unworthy" champion.

None of this is to say that the complaints weren't valid. The map didn't do a very good job of showing where the thick stuff was. That's a problem, especially in a long course event where route choice decisions are crucial. Still, it was nice to realize that the aspect of orienteering that used to be my undoing is now a strength. Just goes to show that you can change things rather than just accepting them.

5/8/07 Mapping

I have to make a new map of Tower Grove for the sprint series. Since I've only got a few days to do it, I'll be cutting a few corners. So, for the next few days, I'll write about how to make a map on the cheap.

For starters, grab some satellite photos off the web. You need enough resolution that you can see trails, streams, big rocks, etc. I find that half-meter (1 pixel = .5m) resolution is usually sufficient for parks. This is the first big shortcut. For a serious map of a wooded area, you really should start with stereo film photos. That will allow you to make pretty accurate contour lines. Since this is an urban park, I'm going to cheat and approximate the contours from the USGS and then fix them when I field check.

To cover the whole area in one image, I had to make a composite image. The underlying satellite image is also a composite so there's plenty of rounding error going on. This doesn't really matter if you're not using a stereoscope to do the contours. The clip above is from the half-meter bitmap. Clicking on it gives you the whole park as a jpeg at lower resolution.

Prior to loading the image into OCAD, I put hash marks on it in purple so I can easily align it to the OCAD grid. The image is oriented to true north for the moment. That's OK, I'll rotate it to magnetic north once it's in OCAD.

5/9/07 OCAD

You can, of course, draw a map by hand. If you're good, the map might come out pretty nice. However, just about all orienteering maps are currently made using a piece of cartography software called OCAD. In fact, I don't recall ever seeing an orienteering map dated later than 1998 that was not made using OCAD.

The reason for this complete market dominance is twofold: 1) OCAD works quite well and 2) it's free. That's a pretty tough combination to beat. The latest version (9) of the program will set you back a bit, but you can download version 6 (which works fine, it just doesn't have as many advanced features) right from their web site.

OCAD takes some practice and some of the operations are not particularly intuitive. The skimpy user manual and online help don't go into much detail. However, there's a community of users out there, including a group on Yahoo who are generally happy to share what they know.

The bottom line is that every serious navigator should have OCAD. Making maps is a great way to understand maps. By using OCAD, the fruits of your training are useable by others. Even if your first few maps are a bit rough (which they likely will be - mine sure were), they can be used for local practice events.

5/10/07 Base map

Once you've got your photos, the next step is to create a base map in OCAD. The purpose of a base map is to give you as much reference as possible for your fieldwork. In the case of a park map, you can often get fairly close the final product because the features are easy to see from the air.

While you don't want to be sloppy, the cartography for a base map is different from what goes into a finished map. I often don't fill in solid areas such as buildings or lakes. I know I might change the outline and when I do, I'll have to redo the fill anyway. I also tend to put vegetation on the base that I know won't make it to the final. For example, I may note the locations of individual trees, even though I'll probably just map the clump as white woods. That way, if I get there and find that one of the trees is very distinct, I already have it placed on the map. Sometimes I see things on the photos and have no idea what they are. In that case I just use another symbol to indicate the location and figure it out on the ground.

When stealing the contours from USGS, you have to decide if you want to use 3m contours or adjust to something else. For this map, I'm going to use 2m contours. Therefore, I had to approximate where the lines go based on the USGS 3m contours. I just need to keep track of how many contours there are. I'll fix the exact shape in the field. This is important to do even if you stay with the USGS interval. Most USGS contours are pretty rough.

5/16/07 Still on

This last week has been crazy in ways I won't even begin to describe. However, if anybody has been interpreting the silence here as an indication that the sprint might not be on, let me set that straight. We are on for this month's installment of the Third Thursday series. Two sprints for the price of one (FREE!) See you there.

5/17/07 Photo finish

The sprints at Tower Grove were certainly fun to watch. The second sprint was an experiment that went really well. The field was handicapped based on the results of the first sprint. The last six controls were on a 1:1000 ultra sprint map.

Since the times were close in the first sprint, it was essentially a mass start race. The pack split and regrouped several times. Mark Geldmeier took the best route from the second to last control and gained about 10 seconds. Just when it looked like he would cruise to his second win of the series, he suddenly stopped and looked confused. Rick Armstrong had the last control figured out and scooted by. But it wasn't over yet. The run in from the last control was only about 40 meters, but Rick's hamstring popped. About this time, Mark had recovered and found the control. He sprinted in, but missed Rick by 3 seconds.

The clip is from the regular sprint map (click for the whole course). The ultra course is here.

David Welsh set the first course, which meant I got to run one of these things for a change. Unfortunately, David Frei was on an out of town job, so there were no death match consequences. Still, picking up the win gave me 30 points on the NA Sprint Series which might come in handy.

I'll have a better write up (and the rest of the series on mapping) soon.

5/18/07 Tower Grove meet report

... and full results are posted here.

5/25/07 Contour mapping

Well, well, well, seems I've been neglecting the blog. Getting back to the little series on mapping.

The only way I know to wind up with decent contour lines (other than getting them from a good stereo image or doing a full-blown topographical survey), is to walk the line. I like to start with the lowest spot on the map and work up. I walk along the line, drawing my path on the map and then pick out a point on the next line up and start over. As I'm just over 1.8m tall, finding the next contour up with a 2m interval is pretty easy. It helps to bring a hand sighting level along.

Note that, unlike a construction site survey, you really aren't that worried about the absolute correctness of the contour lines. If moving a line up or down a bit does a better job of representing how the terrain appears, then do that.

The clip shows part of the base map with the corrected lines overlaid. You may notice the use of a form line in the upper left portion to represent the reentrant. I generally try to avoid using form lines, but this was one instance where I thought it appropriate. The main contour is showing the slope down to the little stream. The reentrant is very shallow and disappears once the stream bank gets steep. To map such a reentrant as part of the main line would imply that the sides of the reentrant were as distinct as the bank. By using a form line, the reentrant is represented as a distinct contour feature and not an extension of the bank.

Subjective decisions like this are just that. Very good mappers may dissagree on some pretty basic representations. What sets the best mappers apart is that they are so consistent in such decisions that one can infer things about the terrain by seeing which option was chosen as a representation. Maps by inferior mappers, or maps made by committee, may be objectively correct, but still contain less information because such inferences can't be made.

Of course, there are plenty of other things that need to be checked as well. I'll get to some of them tomorrow.

5/26/07 Vegetation

I think my biggest misconception about mapping (prior to making my first map) was how difficult it is to get vegetation right. I'd still say that it's the area I struggle with the most, although I think I'm reasonably good at it (the fact that there were no complaints about the S-F map at Team Trials last year gives me some reason to be confident of that claim).

When mapping an urban park for a sprint, you can take the easy way out and just map everything as orange mesh (open with scattered trees). A course setter won't want to use something as vague as the boundary between a field and a shady area, anyway. However, if you aren't completely rushed, I recommend mapping the trees. It's good practice and it makes for a more aesthetically pleasing map.

As I mentioned on the entry about base mapping, this is much easier if you go overboard on the detail in the base map. If you can make out individual trees, put them on there. Consolidating them into a generalized area of white or orange mesh is easy. Getting the boundaries right without such information takes time. The problem with satellite photos is that they are usually taken at an angle rather than straight down. Thus, even though you can see the individual trees, it's not obvious what part of the ground they are actually covering. If you can make out where the trunk goes into the ground, that's a real bonus.

More difficult is assessing the density of vegetation. The standard I use for urban parks is that white woods is basically fields that are shaded by large trees and anything that we'd normally call "woods" gets some shade of green. Light green is still pretty fast. Medium green is stuff you probably don't want to run through in shorts, but could if you had to. I always save dark green for stuff you really want to go around.

The actual mechanics of mapping vegetation density are largely matters of taste. I use a color-coded numerical system. I map all vegetation in green and then number the area according to the density as follows: 0) open woods, 1-3) light through dark green, 4) open fields, 5) open with trees, 6) rough open, 7) rough open with trees, 8-9) undergrowth (light, thick).

I have a specific (and nonstandard) use for the distinct vegetation boundary symbol. I use it to connote evergreens. I do this for two reasons: 1) evergreen boundaries are generally quite distinct, so they make decent control locations and 2) there isn't any other use of the symbol that I've found very interesting on a sprint map. I do make a note of this in the legend of my sprint maps, but most runners have no trouble figuring it out, even if they haven't bothered to check the key or the course notes.

5/31/07 Generalization

One of the important issues that comes up when field checking is the level of generalization. This is particularly true in sprint mapping where the scale permits you to map a lot more detail.

The trend in mapping over the last 10 years has been towards more detail. I'm not a big fan of this myself, but in the case of a sprint map, I'll concede that more is usually better. I still do stop short of mapping individual trees unless they really are prominent and/or isolated.

For the ultra sprint map at Tower Grove, I decided to go ahead and map every piece of vegetation. The result was interesting in two ways. First, it turned out to be pretty easy to map everything. I guess I hadn't realized how much time I spend making generalization decisions. I mapped the whole area for the ultra sprint in just over an hour (which comes to around 50 hours per square kilometer). That's about a quarter my normal mapping speed but still faster than I would have expected.

It also turned out to be pretty challenging to run on, particularly legs like the one to the right. This leg took me 11 seconds (including time to punch). When leaving #2, I picked up the wrong tree. I adjusted quickly because I had thought to count the number of trees I'd run past. I probably lost about a second, but without the close look at the map going into 2, I would have lost 4 or 5. That's a 40-50% error.

I don't think I'd like to run on such a detailed map all the time, but it was a good exercise.