Surveyor Question - Elevation
 

I am applying for a permit to make a small change to my house.

I won't go onto the very painful details, but I have submitted a landscaping plan showing the elevation of my property for drainage.

The city has basically accepted the plans, with one caveat: they want all my elevations referenced to a city tombstone marker.

None of the tombstones are near my house. I have a manual transit, but nothing GPS connected.

How can I get a starting point for my property? I do not see an elevation on survey.

I could rent a GPS theodolite (I really DO NOT want to do that). I have looked for elevation maps online (I am not in USA), there are some 'rough' maps available, generally with 1.0 meter accuracy. There are also some phone elevation Apps, they appear to be 'close'.

I'm thinking I should get an elevation from my phone at the tombstone, and then use my phone in my yard, and use the difference to adjust all my numbers? I can also cross-check the hone result with an online map.

Anyone got a better idea? Paying $5,000 for a new survey is way overboard for what I'm doing.

**I believe you can get Topos here: https://gdg.sc.egov.usda.gov/

Did you see if any of your neighbors have a plan with elevations?

**You can request data from the town through the FOIA. Have they done any roadwork or drainage within transit shot of your house?

**Edit: Sorry, I just saw your not in USA.

Do you have an existing survey?

If you did and it had an elevation at a curb or storm drain, and you know the elevation of the tombstone, you could back into the elevations for your work using the instrument you have.


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I have a survey from ~1960. It does not show any elevations.

He’s not wrong.

I would use a smart phone at both your property and in a known location and compute the difference and call it a day.

That’s close enough for what the city needs to know.

Yea, agreed. My only concern is using my engineering stamp on erroneous data.

I'm going to use the 'free' info I can get and merge it with known data, then fudge it....

This city process is completely garbage and useless....

Let me guess, the local surveyor is related to the person approving the permits.

You need a consulting civil engineer, not "just" a surveyor. As they say, to a worm in a jar of sauerkraut, the world looks like sauerkraut.

Otherwise you will be caused to survey the entire block. Seriously, all of the streets and major intersections. Your guy needs to advocate why they don't need a corner monument for you to get a permit to install hardscape and irrigation, even a 6 foot block wall with footings.

No. This is a case of city employees sitting at home (still in Covid protocol) and being told to take zero risks and take zero responsibility. No one form the city can look at a drawing and apply logic. They are instructed to look for either an engineer's stamp or the homeowner signing off to take responsibility. But the homeowner can't sign off on drainage, only on structure.

I had an outside civil engineer stamp my initial submission. The city just wants the elevation numbers altered to reflect 'actuals', not 'relative'. No one from the city will leave home to look and think. They want to see numbers that are sufficient to absolve the city if something goes wrong.

Holy *****. You are actually an Engineer with a stamp and seal and you are referring to a known elevation datum point as a "tombstone"?!

Do you know the difference between Doctors and Land Surveyors?
Doctors bury their mistakes, where Surveyors monument theirs.....but rarely* if ever with a tombstone!

Regards,
SCadaddle
Professional Land Surveyor in the USA

* I have, once upon a time, used the corner of a headstone of a one John Henry in a cemetery as a temporary benchmark for my own use.

:rolleyes:

You don't even know where I live, or what terms my city uses for their benchmarks.

So you need to topo the site. I think that's easy to do with satellite data.

State your assumptions then stamp away!!

Is anything being built nearby that has a benchmark you can use?

Didn't you know? In Canada they use dead people for a datum.

Why do you need a permit?

Whose property is it?

My wife is a draftsman for a survey company and in her words, I do 5hit like this all the time…

She says your RPR (real property report) might have an elevation. What province are you in? She might be able to help. Each municipality has different expectations and requirements. There should be all sorts of benchmarks you could use to establish elevation.

Worst case, she says it’s $1500 - 2000, not $5000 to get this done.

Anyway, if you PM me your contact, I could ask her to help you out… depending on what province you are in.

I poked around a bit on the googler just to see what you Canadians have up there with regard to something similar to FEMA, Flood Insurance, Maps and Elevation Certificates like we have down here in the lower 48, eh.

I didn't find too much.

So here's what you do, if you are an engineer and trying to save a buck by doing what you can do yourself with your transit or GPS Theodolite or whatever. IF a local Surveying outfit can perform an Elevation Certificate for you, doesn't matter if you are in a flood zone or not, for that matter here in the lower 48 the Continental Divide in the Rocky Mountains is in a "Zone X", that would probably be pretty reasonable. I'd think 50 cents on the dollar compared to the $1500-$2000 dollars mentioned above. Then, with the Certificate you'd have a real elevation established on the finish floor of your lovely abode. Probably other elevations such as lowest and highest adjacent grades as well. Numbers you can work with. Real numbers. And you've got a Surveyors stamp/seal and signature on the documents that are now your metadata.

Remember, metadata is data about the data.

Do your thing draw your map provide the metadata to back it up. Done.

GPS is very good on location of X and Y with in 0.01/3 of a foot time after time

not so much on Z elevation for a lot of odd reasons inc the MOON [tides on land !] can be off more then a 0.2 of a foot correct level run should check in at under 0.03

level runs I have done too many miles
and found government bench marks out [beach sand bars are not real stable even after built up

the tool to do accurate levels is not GPS OR A THEODOLITE but a good old fashion level and a fancy stick new stuff self reads and records but looking and reading the numbers works fine
streets are layed out to elevation center line or back of sidewalk if one should be known
if sanitary sewers the manhole are dead accurate and known/listed
a house plan should have a floor elevation listed

if you do not have any of that you can find listed
GUESS it can't be too far off and who will check ?