I doubt they care about xy for the houses, level them, xyz of course for the manholes with inverts and field book drawings
MightyMoe, post: 443478, member: 700 wrote: I doubt they care about xy for the houses, level them, xyz of course for the manholes with inverts and field book drawings
I suppose that a position with a handheld recreational-grade receiver would be good enough to identify everything leveled: manholes, TPs/TBMs, and entrances to houses, but I tend to doubt that it would be very more work to run a 3D traverse with one person and a reflectorless total station than to level it. The simple method would be to leave two prisms/targets on control points at 700 ft. intervals or less and just resection to locate the intermediate stations from which the heads of doors or other features on the houses were taken.
Assuming 50 ft. lots, that would be more than 10 setups per section between higher-order control points. That would be more than adequate to give a very good elevation difference between the control points, for which, if GPSable, GPS-derived positions should be perfectly fine if properly connected to some datum.
Ohio Surveyor, post: 443421, member: 12195 wrote: What is the fastest way? How would you do it?
I doubt that I would be doing it the fastest way. Not as my primary concern, anyway.
I'd use RTK to get the manhole barrel locations, and GIS data to get the house locations. Then I'd level through the manhole rims, running side loops off the rims to floors.
Kent McMillan, post: 443479, member: 3 wrote: I suppose that a position with a handheld recreational-grade receiver would be good enough to identify everything leveled: manholes, TPs/TBMs, and entrances to houses, but I tend to doubt that it would be very more work to run a 3D traverse with one person and a reflectorless total station than to level it. The simple method would be to leave two prisms/targets on control points at 700 ft. intervals or less and just resection to locate the intermediate stations from which the heads of doors or other features on the houses were taken.
Assuming 50 ft. lots, that would be more than 10 setups per section between higher-order control points. That would be more than adequate to give a very good elevation difference between the control points, for which, if GPSable, GPS-derived positions should be perfectly fine if properly connected to some datum.
As far as the house locations go; they have those already. It sounds like they need a good elevation but they will attach those elevations to the figure for each house already in the GIS, of course I'm guessing a little, a chat with the client would confirm this. The manholes do need good XYZ. Setting some xyz bench mark control and running levels would probably be faster than lots of setups with total stations or a robot for locating the houses, and it accomplishes the task needed. For manhole elevations level them since it's out already, xy with a TS or GPS.
Ohio Surveyor, post: 443421, member: 12195 wrote: Hello all.
I have an idea of how to do this job, but I wonder if anyone else has a better way.Residents in a city are having sewer backups during heavy rains. The engineer is building a hydraulic model to analyze the situation. There is GIS data available, but we don't know how good the GIS sewer rim and invert elevations are. In addition, we need to add basement elevations to the hydraulic model.
My task is to make a profile of about 2 miles of sewer, with the addition of front door sill elevations of several hundred houses. The engineer will subtract an assumed distance, say 10 feet, from the door sill to the basement. So, I need good elevations of manhole rims and inverts, and door sill elevations, all with approximate horizontal coordinates.
This is in an area where most of the houses are close to the street, and many of the houses have deep front porches surrounded by landscaping. So, it may be necessary to set up directly in front of the house to get a shot on the front door sill. That's a lot of setups.
I have an optical level and level rod, a robotic total station and prism pole, and a GPS receiver. The robotic total station has both a laser pointer and a reflectorless feature. I have access to the GIS, from which I can pull horizontal coordinates but not good elevations. I will most likely be working by myself, though I may be able to get a second man if I can show that it is more cost effective.
I can think of many ways to get the work done. What is the fastest way? How would you do it?
R
If accuracy is not critical, RTK on front walk and use a hand level to measure up to door sill.
You are apparently assuming you can be loose on the door elevations because the engineer is assuming 10 feet. However, there may be a home that comes in very close to making grade. Murphy's law says they will measure, without contacting you, exactly from the door to the floor to decide the home makes grade. After construction it will be discovered you showed a higher door than reality, because, after all, approximate elevations are good enough. Someone will now have to pay for the pump to service this house. Guess who may get that privilege?
The original post makes it sound like you already have this project. If so, are the accuracy standards specified? If not, I suggest you have the accuracy requirements verified, in writing, before going further.
Ken
Ken is right on.
Ken Salzmann, post: 443517, member: 398 wrote: You are apparently assuming you can be loose on the door elevations because the engineer is assuming 10 feet. However, there may be a home that comes in very close to making grade.
That's true. Another consideration is that there could be different floor models for these homes where they could be split-level, or the entranceway, or foyer, is raised, or lowered, in respect to the main living areas. That seems like that would affect the engineer's decision to apply an arbitrary 10' to the sill elevation.
I did this type of work in the early 70's.
1) leave a pk nail at each house, hopefully a driveway. Pk nail has coordinates, and good elevations on it.
2) take a rag tape, measure from the pk nail, up the driveway, and eyeball the distance to the part of the house where the door is. This will give the engineer the run distance from the sewer line to the house.
3) run levels from the pk nail, up the driveway, turn on the door sill, ( turning on the door sill is important, no side shots, elevations are most important here ) and back to the pk nail.
This goes pretty quickly.
Ohio Surveyor, post: 443421, member: 12195 wrote:
Residents in a city are having sewer backups during heavy rains. The engineer is building a hydraulic model to analyze the situation. There is GIS data available, but we don't know how good the GIS sewer rim and invert elevations are. In addition, we need to add basement elevations to the hydraulic model.
You can study the situation all you want, but until you get the residents to disconnect their sump pumps from the sanitary sewer system you will have an overloaded system every heavy rain.
Municipalities around here are very strict about that. Sump pumps must be connected to the storm drain system not the sanitary sewer system.
Thanks for all the responses.
1) Let the engineers do the estimating and the assuming
2) I would never NEVER ever assume a constant for doors or doorknobs, especially in an older neighborhood. Things get replaced.
3) Good luck with your project!
So, I started this job last week. I spent a day and a half opening manholes with one other crew member. We opened 60 manholes in 12 hours, and about 20 of those manholes required traffic control. I'm scheduled to start leveling tomorrow. My goal is to get a proper elevation measurement on each door sill, using a conventional optical level, a level rod, and a two man crew.