Register | Login
Attackpoint - performance and training tools for orienteering athletes

Discussion: Map assessment

in: Orienteering; General

Feb 21, 2011 6:15 PM # 
iansmith:
I am assessing about sixty maps in an effort to prioritize mapping efforts, and I'm struggling coming up with an objective measure of map quality. How do you assess the quality of a map, and given a large number of maps, how can a prioritization be devised? The number of maps makes the problem harder, because it's not practical to assemble a committee and visit all the maps systematically.

The eight broad criteria I'm currently using are:
  • Existing map quality
  • Vegetation
  • Terrain quality
  • Difficulty obtaining permission from landowners
  • Parking accessibility
  • Size of accessible area
  • Distance from population centers
  • Intended use

Landowner permission, parking, size, distance, and intended use can be quantified somewhat objectively, but existing map quality, terrain quality, and vegetation are tricky. I would further decompose map quality into accuracy of contours, accuracy of mapped point features, trail network completeness, and the completeness of the map overall.

Comparison with "truth" is an attractive sentiment; LIDAR data is typically much more accurate than base maps made from orthophotos aerial stereophotos twenty years ago, and an objective comparison can be made. In the absence of LIDAR, it's a harder problem.
Advertisement  
Feb 21, 2011 6:59 PM # 
jjcote:
Did you go to MIT or something?
Feb 21, 2011 7:46 PM # 
Tundra/Desert:
an objective measure of map quality

Crowdsource consumers to vote. Their subjective perception is the metric you are looking for.
Feb 21, 2011 8:38 PM # 
Jagge:
How about using analytic hierarchy process, values based on the vote data?
Feb 21, 2011 9:34 PM # 
TheInvisibleLog:
Cull the obvious ones (access issues, boring terrain etc). Then design a paired comparison assessment by consumers and scalogram analysis.
Feb 21, 2011 9:37 PM # 
VO2 Orienteering:
Ian, the way to count the map quality is easy in my point of view.
You have to divide your 60 maps into 3 category-
1. park maps (sprint maps, city areas),
2. 80+% white forest / 80+% field maps (those maps do not have to much vegetation, so they change only as trails and contours- vegetation does not change in more then 5 years) and
3. others (maps with high vegetation, which is changing with 5 years).

So, for park maps and others you give 5/5 at the first year it was mapped/revised, and 10/10 to the second group. We have to assume that the mapper did a good job though. Every year you put the evaluation down by one.

For example, if the sprint map (group) was mapped in 2007 it will have 1/5 this year, so next year, you better not use it before updating and making it 5/5 again.

Ian, you can make your own scale out of 100 or anything else. It is the nature of the map to change. Some of them change faster then others, so think you can measure the map quality just by the year of its last update and scale, in which it is categorized.
Feb 21, 2011 11:00 PM # 
mikeminium:
I guess any seasonal use restrictions would go in with ease of access.

For some areas, size (km2) alone is not as important as the shape and ease of use; some large areas have serious bottlenecks or shapes that limit the usable area.

Areas with dense mountain bike trails seem to change almost constantly at least in our area. Maybe not so often in parks which carefully monitor the trail development.
Feb 22, 2011 12:26 AM # 
gruver:
There's no objective way.

I did an exercise for my club last year. Identified 19 maps that we might do something about. They included big and small, some tantalising and some stupid (you always get half-arsed ideas coming up from people who have no idea.) Categorised "value" of possible improvement as low/med/high. Categorised "effort" of bringing it up to modern standard as low/med/high. Also listed special factors for each map.

Then listed two groups of maps: 1. Value higher than effort (high/med or med/low etc) 2. Value equals effort (high/high, low/low etc). This listing carries with it the statement of special factors, which may end up determining action anyway. But at least there's a group of maps to look at first. And a second group that might be worth doing something about. And (by omission) a third group that its not worth looking at.

OMG, just found myself working on a map that didn't even get listed. Such are the risks of any sort of system...
Feb 22, 2011 2:22 AM # 
giovanni:
Team goals are also important in priorityzing mapping work. Are there plans for recruiting people teaching orienteeing ? Then you need new or updated maps close to where the teaching will be. Plans for improving people skills? Then you need good maps close to where team members are to facilitate training. Plans to hold A-meets? Then you need interesting areas that can challenge competitors and offer good logistics.
Feb 22, 2011 3:49 AM # 
EricW:
One issue I don't see mentioned is the availability/cost of lodging and transportation for the mapper. In my experience, at a practical level, this is often the #1 factor in getting a map done, especially in more rural settings. It often comes down to a motivated individual or family who is local to the terrain. This is also an indicator, albeit imperfect, that someone will make sure the map is put to good use.

Its becoming useless information, but orthophotos were rarely used for O maps 20 years ago, and certainly had nothing to do with contours. Uncorrected stereo photos are the basis for photogrammetry, from which most serious O maps were made in the last 30- 40? years, before lidar.

This discussion thread is closed.