I have used gps and wheel.The weel can be off on high grass or rough terain. Like a 5 -10 or so yardsor more .I have a gill wheel.When the wheel goes over a bumpy course with wet grass i find it off.What should i use ? This is only to mark speed workouts on the grass.The wheel does seem to work on the road. Should i stick with gps ?That is what we used last year and it worked out fine.
from my limited experience, GPS prob sucks, so the wheel for sure, or a bike, & do the best you can with the terrain
on page 34 from USATF course certification guide, just read this:
"Measuring on Dirt, Grass, and Sand
Avoid laying out a course over non-paved surfaces. If you must, minimize the distance to
be measured over such surfaces. Hard-packed dirt is OK, but avoid sand, soft dirt, and deep
grass.
The greatest accuracy is obtained by steel-taping all non-paved sections. However,
measuring the entire course with a bicycle calibrated on a standard, paved calibration
course is acceptable and is, in fact, the recommended procedure since it reduces the chance
of error.
The calculations (for start, finish, splits, etc.) can get quite complicated if you piece
together a course measured partly by bicycle and partly by steel tape. If you do this, make
permanent marks at those points where you change between bicycle and tape
measurements.
When you ride the bicycle over non-paved sections, you will tend to get fewer counts than
you would riding over the same distance on a paved surface. This will tend to make your
course slightly longer. Measuring on firm dirt should not lengthen that part of the course by
more than 0.1%; measuring on grass may lengthen that portion by 1% or more; measuring
in loose sand may lengthen it by more than 3%.
Measuring dirt roads usually presents little problem if the road is well graded. If the non-
paved road is not graded (usually two ruts) and is winding, it may be virtually impossible to
ride the shortest possible route since the proper route would cross the ruts and intermediate
ridge at angles which do not permit safe riding. If such sections are encountered and cannot
be avoided, they must be steel-taped. "
I don't think the GPS will work unless the course is extremely flat. If the course is hilly, the GPS will probably measure the course "as the crow flies" which is obviously a much shorter distance than actually going up and down hills. Unless the GPS can measure the lines draped over an accurate digital elevation model (DEM).
From, a GIS expert. You're welcome.
Just so I understand the question, you're not talking about an actual cross country course to use in meets but some straight grass stretches for speed drills?
Blamo McBlamo wrote:
I don't think the GPS will work unless the course is extremely flat. If the course is hilly, the GPS will probably measure the course "as the crow flies" which is obviously a much shorter distance than actually going up and down hills. Unless the GPS can measure the lines draped over an accurate digital elevation model (DEM).
As a GIS expert, I presume you would be aware of how little changes in elevation affect the measured distance of a course. You know, basic high school trigonometry. Say you had a 10 mile course that had an average grade of 10% (rises/falls 10 feet every 100). The differential between your flat measurement and your 3D measurement would be 0.05 miles, or about 264 feet. Can you name any course that has anywhere near that level of average grade?
And how do you know GPS don't account for altitude changes? Their whole basis of operation is dependent on knowing where they are in 3D space, not a flat, 2D map.
It's a workout. 100% accuracy of the distance is irrelevant.
Repeat the workout. What happens? Faster? Slower? That's important. More reps at the same pace, less rest? That's important.
Step 1: Jog the course you want to set up splits or total distance for.
Step 2: Run this course at a decent effort. Make note of specific time markers (ie: 30s at the bush, 90s at the turn, etc).
Step 3: These are the marks you use during your workout.
I've had courses that were measured mile to mile and I knew if I passed a random checkpoint in a certain time that 9 times out of 10 I'd meet the time I wanted at the mile mark. I've also had random interval courses in which if I hit certain workout splits I'd be in pretty good shape to race.
It doesn't have to be rocket science. You're either improving, stagnating, or getting worse relative to your previous efforts.
Alan