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?
[SARCASM]Just shoot the finish floor of the basement with your Javad GPS.[/SARCASM]
Roughly how many door sills are we looking at in that two miles. Assuming both sides of the street are lined with single family housing. Or are many of these commercial and multi-family units that eat a lot of linear space with only one door sill? Could a full city block be shot from one point near the middle or are there large vegetation-type obstacles much of the way?
In all seriousness, it sounds like a scanner will be the fastest and most accurate.
You (probably) don't need to see every door opening.
Houses generally are level and up right and you can use those attributes to interpret the elevation of the door sill, floor level to a place where you can measure.
If it's brick or horizontal board cladding it's a piece of cake to do that.
If the engineer is assuming 10' and he's happy with that it does leave you freer to make these interpolations and still be better than 1" difference if you setup at each entrance.
A long spirit level can help too.
It will still be tedious.
I'd take a second person if I was doing it.
I code my floor levels with house number appended.
No 25 Street is FL 25
There's a lot of people involved and need to be prepared for questioning, dogs, probably favorite bushes and plants that you don't dare touch or 'lightly prune'.
Has the community been letter dropped?
That's helpful and can save you time.
I've done similar for floods and the Council sent letters to all the residents.
It helped immensely.
How close do horizontal cords need to be. If +/- 5' and it's a cardinal direction street and most houses have approximately the same setback could you just shoot the back of walk at the carriage walk and add or subtract northing or easting in a spreadsheet. Then snag another guy and just level in sill elevations if you can't see 1/4 the block from one setup with a robot I would think this would be faster.
Hybrid GPs and Robotics
I need to shoot over 200 door sills. I might be able to get as many as 4 in one setup. The city is going to drop letters so I don't see any issues with getting access to the doors. Most of the mailboxes are near the door, so they are used to people walking to the door.
Horizontal coordinates are not critical at all; I was thinking of taking a paper GIS map with me that shows houses derived from controlled aerial photography and spotting the door sills on the map. Then, in the office I can pull coordinates from the GIS for the engineer to use in his hydraulic model. Really, he just needs to show basements in the profile. Or, I can just run a conventional traverse, but I'm trying to do this as efficiently as possible.
We run a similar problem.
We run RTK control.
Then level through it.
The static the major control.
We resect from the control to tag 1st floors.
Then we mobile map the whole route.
At some point we mark and RTK utilities.
At some point we setup on the control and tag some monuments.
Take bits and pieces.
Doesn't it make sense to flag drainage as an illicit discharge? We have not had drainage to sewer here ever. They caught an illicit discharge a few years ago when a jet overshot the runway, ended up in a parking lot and leaked some fuel that wound up at the plant.
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I think I'd try shooting the door knobs or top of the door. Be a lot easier to see and shoot reflectorless and distance down to door sill should be standard. Shoot the manholes robotically. Set enough control points somewhere along the street or sidewalk with gps so you can see a couple and do a resection from wherever you'll have to set up. Run levels through them if they need to be more accurate than .04'. I'd first decide where the setups would have to be, then set control accordingly. I'd also forget about the gis mapping.
I've done a similar project on a larger scale and if we couldn't see the door, we'd shoot a point on the siding or bricks and measure up/down to the FF. Throw that measurement into your HR so you dont have to do any processing. I think you'll make quicker work of it than you think once you get rolling.
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?
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?
Personally, I would run a traverse with vertical control. Not being able to see the typical housing or the street, I am taking a stab in the dark here. Setting control with an imaginary baseline relevant to centerline you could take shots at the curb with offsets left and right either by description in the offset menu for rough door locations. When the door sills are not viewable from your set up, take elevations relative from the bottoms of the siding or from bottoms of windows if brick and physically measure to finish floor. From the control you can also obviously take shots on existing storm structures. And you will have it when/If you need to come back to dig up buried structures or any added info the engineer will request later.
Might want to see if all exterior doors, or hell most doors, don't have a standard height and work down from there. If the engineer is just guessing at basement floor elevations, why can't you estimate door heights ??
Are you required to note whether or not a basement exists on each property shown?
R.J. Schneider, post: 443454, member: 409 wrote: Might want to see if all exterior doors, or hell most doors, don't have a standard height and work down from there. If the engineer is just guessing at basement floor elevations, why can't you estimate door heights ??
Ugh .. incomplete reply there. If you could shoot the tops of the doors - what might be visible above the foliage .. whatever - you could then subtract a standard door height.
March down the street taking RTK shots as needed, and leaving PK nails in likely places with a spot (spot, not huge circle) of pink paint by each one. If in doubt, set more points than needed. Write the point number on the nearby curb or sidewalk with a black marker in small numerals. Later, run a line of levels through the PK nails, then occupy as many of those control points as needed with a reflectorless total station, shooting a marked strip of masking tape a standard 5' above the door base.
Are you likely to be back later for those 'Oh, we now need......' moments?
I quiz the requestor when I get a job like this.
Too many jobs end up with add-ons later as the job progresses.
Also are you likely to get more jobs in vicinity?
I look at that prospect and throw in extra control anyway, even tieing into any visible other survey marks along the way.
Add them to my survey data for later use.
Working for myself I can afford any additional time involved which has repaid itself on many occasions.
The answer to these questions could influence your method.
eddycreek, post: 443445, member: 501 wrote: I think I'd try shooting the door knobs or top of the door. Be a lot easier to see and shoot reflectorless and distance down to door sill should be standard.
Yes, that's exactly what I was thinking. If the distance to the basement is to be some assumed value, then the exact elevation of the door sill is hardly critical.
If there is lots of tree cover or the setting is otherwise problematic for GPS, I'd just plan on 3D traversing through control points with GPS-derived checks at intervals for N,E, and Elev, adjusted, of course, in Star*Net or some other off-brand LSA software.
Masking tape, @5' up, w/ pinch of dot tape on it. On every door, or near the door. Make yourself some sticks, with targets, you can place, in spots not suitable for dot tape.
Any particular "problem houses", maybe use a tube level, with water in it, to check basement levels.with stiff box tape. 3 extra days.
Use pk nails, and x's in curbs, set up so that one setup can get 4 to 6 dwellings.
At 4 houses per setup, and 200 houses, thats 50 setups.
Figure one trip through with rtk. 4 min per shot. That is easily done, with rtk.
Then, the reflectorless to the houses.
A double level run is ideal. 2 man crew is way better for this.
All manholes. Storm sewer. Dip structures.
All said, 2 days on level runs, to get accurate vert ctrl.
5 - 6 days on reflectorless. (factor in the social side, chatting, dogs etc)
2 days on rtk.
5 days dipping structures, and inverts.
Buy star*net, to integrate it. And, to help track uncertianties.
Do it all spc.
Draft it up. Integrate with GE, or hwy dpmt aerial photos.
Do a bang up job. Pretty plat.
Poop flows downhill.
Get paid well.
Take a mini vacation, when done.
Let know how it went. Post a few pics.
Don't get hit by a car!
N
Even if you can only get 2 houses at 5 minutes a setup, thats 500 minutes for 2 guys with a level. Control can be dropped at each end and a few points for error isolation in the middle. Out of there in two days tops.
