Geolocation

Before I get to involved in trying to make this work, how accurate is the geolaction function. What I am trying to do is layout light pole bases in a parking lot. Normally we do this after the site contractor has staked out all the curb lines. On this job that might not happen for a while, so to keep things moving, we would like to layout the light bases now and get the conduits and bases in.

The background civil drawings that I have, have a geo marker in them. Although the map seems to overlay into the right spot, the markers are in different locations in the different drawings. One is a county away, one is in a state away and one is out in the ocean. I messed around and tried to reset one to a Lighthouse less than a mile away. That has me wondering that if I do reset it, how accurate would my location for the lighthouse be? Could I use a handheld GPS and put a marker off the building, and then measure to two spots on the building?

In the end I would like to add points on all the light pole bases with their geolocation, and give that to a surveyor and have them mark out all their locations in the field.

Any thoughts? How would you tackle this part of the job?

All your drawings should be on the one co-ordinate system. Ie known common points on each dwg. Just because the marker says its at x,y is it really ? Have the drawings been altered using new UCS we work all the time in 2 real world "World" and local generally to realign roads to horizontal or a better fit. All set out though is done in World.

Re handheld gps any where from 15m to about 1m, mobile phone photos where 6m away from where taken not to bad.

Thanks for your reply.

All the A&E drawings use 0,0,0 as the origin for each building, like they usually do. I am not sure what they used for the origin on the civil drawings, but they do line up with themselves, but they are at a different scale than the Arch drawings.

There are three buildings on this site. The light poles surround the buildings. There are a few between the buildings on the short roads that connect the buildings.

My thought was to dimmension between bases, including angles. Also dimmension some of them back to two corners of the building, including angles. I would think that a surveyor should be able to work with that. When the bases are along sidewalks they are usually 6 to 12 inches back, so being a meter of is to much. That's why I dont think the GPS thing would work. I would like to put a GPS benchmark out there just to see if the numbers wuld be close to the same.

I think the whole thing is going to wait. My boss is going to talk to the sanitary contractor and see if he can mark it out for a price.

I wont go into to much but sometimes we access the landscape plans and they are in mm where we are true world in metres so 1st we scale back to meters then move the whole project. 99% of the time this is ok as they do not put a rotation on the plans so up is still true.

GPS benchmark can be a can of worms its not as straight forward as it sounds I am not a surveyor but the effect of GPS v's planar survey can introduce its own set of problems, generally if you talking a building and a car park the errors will be very small maybe mm's so not a problem.

Getting some one to do some real world ties would be a good idea.

Many of the old bridges were built from both sides and met in the middle they did not have GPS to help them.

Before I get to involved in trying to make this work, how accurate is the geolaction function. What I am trying to do is layout light pole bases in a parking lot. Normally we do this after the site contractor has staked out all the curb lines. On this job that might not happen for a while, so to keep things moving, we would like to layout the light bases now and get the conduits and bases in.

 

The background civil drawings that I have, have a geo marker in them. Although the map seems to overlay into the right spot, the markers are in different locations in the different drawings. One is a county away, one is in a state away and one is out in the ocean. I messed around and tried to reset one to a Lighthouse less than a mile away. That has me wondering that if I do reset it, how accurate would my location for the lighthouse be? Could I use a handheld GPS and put a marker off the building, and then measure to two spots on the building?

 

In the end I would like to add points on all the light pole bases with their geolocation, and give that to a surveyor and have them mark out all their locations in the field.

 

Any thoughts? How would you tackle this part of the job?

As a licensed Surveyor I prefer you to give me those drawings in the coordinate system they were created in referenced to a few known control points for both horizontal and vertical. This way I could easily xreference it into a drawing using a local coordinate system which for me would be Florida's North Zone. I would lay it out using coordinates from that drawing. As the world is not flat there are several different projection types that make up the hundreds of coordinate systems that come installed with Civil 3D.