Hi, I'm looking for some comments on a plan I have before I purchase some equipment. Still learning the basics, so forgive my ignorance.
?ÿ
I want to generate a topographic map of an estimated 20 acre watershed for pond construction calculations, and for fun. There are no available existing topo maps of the area. There happens to be a TruPulse 200 for sale locally for only $200, and I also plan to buy a decent compass (looking at a $80 suunto, but suggestions very welcome). The property survey indicates elevation from sea level of one of the corner metal posts so I would start there. I've been using QGIS to map fictional coordinate and elevation change data, like the data I plan to obtain using the below plan, in order to get comfortable with the software and practice generating topo maps from scattered points.
?ÿ
The plan:
I would use a helper wearing an indicator on them the same height as my eye level. Using the compass, I would have them proceed roughly along the bearing indicated by the property line, in my field of view, for 20 or 30 meters, if on relatively flat ground. The TruPulse would then be used to find the horizontal distance and elevation change between me and them. I would input that into my spreadsheet on my tablet (which produces XYZ coordinate data relative to start point). I would then walk to where they were standing and they would proceed again along roughly the same azimuth. As it varies in order to go around dense vegetation, I would indicate the new azimuth. The spreadsheet I have accounts for this when generating the XYZ points. When on very undulating ground, maybe only 10 yard progressions would be made in order to get better resolution of the topography - It's nice to see where seasonal creeks run. After maybe 50 or 100 yards of this, I would take a 90 degree turn, proceed back the way we came, a final 90 deg turn, and return to the start point, to complete a closed rectangular traverse. This would allow obvious mistakes to present themselves when the data is entered in and the first and last points are outside a reasonable margin of error (they should be the same). I would continue these rectangular closed traverses, maybe staking out the corners or marking a tree at the corners so I know where to proceed from for the next traverse.?ÿ
Here is a picture of what 'The plan' could look like:
Here's a screenshot of the excel sheet that takes the relative measurements and produces actual XYZ coords. My starting lat/lon removed for privacy.
Is it better to go in long strips? Am I way off thinking my compass will provide an accurate enough azimuth (it says +/- 0.5 deg...)? Is there something blatantly obvious I'm missing here? Thanks for any advice.
You need 3 pieces of data for each point that you use to make your surface. Distance, Bearing/Azimuth, and vertical change. Your method should work. A hand level and 100' tape and a rod to reference height could substitute for your TruPulse. As long as the ground isn't extremely flat, you should get results that would allow for a pond to be designed and built. Making squares as you cover the ground isn't necessary but it does allow you to have a sanity check on your vertical results. You could accomplish the same by checking a previously located spot periodically.
My plan would be to get a good dozer operator to look at it and help layout the location of the pond you want.?ÿ I dare say there have been as many ponds designed and built from the seat of a dozer as any other way.?ÿ?ÿ
How big a pond? Is it a pit or a reservoir/dam, or a combination?
@lurker I hadn't heard of a hand level before, thanks for the suggestion. It would certainly be more economical if the TruPulse deal doesn't happen. And thanks for the reassurance.?ÿ
@fairbanksls Agree 100%. Still looking to track down someone who has done this sort of work before. I want to do this survey regardless, but there are still test holes to dig (hopefully find clay) and research to do yet for this pond.
@mightymoe Probably would need discussion with the operator or an engineer but just eyeballing it I think there is an acre basin that could have a dam put in.?ÿ
If this is just some fun side project I might look to borrow or buy a used auto level/rod, a compass or a tape for laying out a 50 or 100 foot grid, and topo it that way.
Grid plus be sure to get the peaks and valley line.
1 acre surface area, in my state you need to permit any impoundment that is more than 1 acre feet in volume. But, I'm guessing that's not a thing where you are, I don't know that for sure.?ÿ
But, if it's only 1 acre surface area then you aren't going to meet the safety of dams regulations and those will apply anywhere. Be sure whoever is building this impoundment understands local regulations.?ÿ
If this is just some fun side project I might look to borrow or buy a used auto level/rod, a compass or a tape for laying out a 50 or 100 foot grid, and topo it that way.
Yep, no money changing hands, just me in the bush messing about, learning. Who knows, maybe I'll even come across a spring. Can you or @bill93 elaborate on the grid way? I've seen steel tape measures for sale, would I get one of those, lay it down parallel to the property line at some distance, then every 50 or 100 feet along the tape would I branch off adjacent to the steel tape for maybe 50 or 100 feet, making sure to take more frequent readings as I come across obvious peaks and valleys?
@mightymoe Good point to bring up about regulations. As long as it's 1 acre or less, not bypassing a stream, not impounding a stream (tell that to the beavers...) and not on a floodplain, I am good to go. There are stricter regulations nearer civilization. Of course, I want to work with a qualified professional as much as possible, if there's something I don't know the sooner I can find someone the better.
?ÿ
Thanks for all the comments! Very happy I came across this forum.
April Fools??
A cheaper fiberglass tape is more than sufficient for your purpose
Licensed Land Surveyor
Finger Lakes Region, Upstate New York
