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Thread: Best Practice for search coordinate export: elevation setting?

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    Default Best Practice for search coordinate export: elevation setting?

    Hello everyone. Obviously, you can see I'm new around here. Most of my work is in the Denver, CO area. I have been a C3D user for about three years now and have wondered about this question for a few months, but did not see any previous discussion here regarding this topic or at any other support sites:

    Like many surveyors, one of my workflows involves creating a model from an existing subdivision or a metes & bounds parcel description for the purpose of creating search coordinates to export to my field equipment as a tool for finding, then surveying the actual position of corner monuments. My deliverables mostly involve boundaries and rarely topo or grading. I've not seen it to cause an issue, but does anyone have pros or cons either way I should be considering regarding the input elevation for COGO points being created for this purpose. More often than not my jobs are of limited geographic extent and are set as "No Datum, No Projection". Only when I'm working in mountainous areas, where the relief from one end of the job can be substantial do I go to the trouble of taking an aproximate elevation for points from Google Earth. Otherwise, when the terrain is fairly flat, I export my points with the elevation set as either a null value or 0.00. When I'm using a conventional total station, I can work in either 2D or 3D mode and there is no issue; however, when doing this with GPS and the Z value for all of my points is 0, my coordinate delta display as I near a given point might show something along the lines of "N: 0.17 ft, E: -0.05 ft, Z: -5127.78 ft". My thinking is that as long as I don't attempt to use the point for a vertical calibration (for those of you who work with Trimble gear and are familar with the meanings of horizontal and vertical calibration) there should be no problem, aside from that huge delta for the Z value stored in my data collector. Of course the new coordinate from the field location of the monument will have new values, including a correct Z relative to the elevation datum I've selected by that time. I also normally create an offset, such that search Pt. #152 becomes field Pt. #1152. So, should using the bogus value of 0 for a preliminary elevation cause me to lose any sleep?

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    Default Re: Best Practice for search coordinate export: elevation setting?

    HI from Oregon
    I have much the same process doesn't bother me. I create the points with 0.0 elevation export them. Unless of course for some reason we are doing something on SPC or another specified Datum then I use the supplied elevations if none are available we use 0.0

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    Default Re: Best Practice for search coordinate export: elevation setting?

    Quote Originally Posted by Layer zero and three-quarters View Post
    Hello everyone. Obviously, you can see I'm new around here. Most of my work is in the Denver, CO area. I have been a C3D user for about three years now and have wondered about this question for a few months, but did not see any previous discussion here regarding this topic or at any other support sites:

    Like many surveyors, one of my workflows involves creating a model from an existing subdivision or a metes & bounds parcel description for the purpose of creating search coordinates to export to my field equipment as a tool for finding, then surveying the actual position of corner monuments. My deliverables mostly involve boundaries and rarely topo or grading. I've not seen it to cause an issue, but does anyone have pros or cons either way I should be considering regarding the input elevation for COGO points being created for this purpose. More often than not my jobs are of limited geographic extent and are set as "No Datum, No Projection". Only when I'm working in mountainous areas, where the relief from one end of the job can be substantial do I go to the trouble of taking an aproximate elevation for points from Google Earth. Otherwise, when the terrain is fairly flat, I export my points with the elevation set as either a null value or 0.00. When I'm using a conventional total station, I can work in either 2D or 3D mode and there is no issue; however, when doing this with GPS and the Z value for all of my points is 0, my coordinate delta display as I near a given point might show something along the lines of "N: 0.17 ft, E: -0.05 ft, Z: -5127.78 ft". My thinking is that as long as I don't attempt to use the point for a vertical calibration (for those of you who work with Trimble gear and are familar with the meanings of horizontal and vertical calibration) there should be no problem, aside from that huge delta for the Z value stored in my data collector. Of course the new coordinate from the field location of the monument will have new values, including a correct Z relative to the elevation datum I've selected by that time. I also normally create an offset, such that search Pt. #152 becomes field Pt. #1152. So, should using the bogus value of 0 for a preliminary elevation cause me to lose any sleep?
    So, you're creating maps that you know up front are based on invalid information, and generate bogus data? Dunno about losing sleep, but losing jobs? That seems likely.

    Anyone who provides me with a survey that is NOT on state plane, and uses bogus elevation data, does NOT get hired again.

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    Default Re: Best Practice for search coordinate export: elevation setting?

    Quote Originally Posted by cadtag View Post
    So, you're creating maps that you know up front are based on invalid information, and generate bogus data? Dunno about losing sleep, but losing jobs? That seems likely.

    Anyone who provides me with a survey that is NOT on state plane, and uses bogus elevation data, does NOT get hired again.
    You do realize the point data being generate for this task is for the field crews in the field to better locate the missing information, correct?
    If you have a technical question, please find the appropriate forum and ask it there.
    You will get a quicker response from your fellow AUGI members than if you sent it to me via a PM or email.
    jUSt

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    Default Re: Best Practice for search coordinate export: elevation setting?

    Well, maybe that's a valid rationale for creating maps with deliberately bad data, but that's doesn't mean I have to like it. Crud creeps, and GIGO is pretty much a universal law of nature.

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    Default Re: Best Practice for search coordinate export: elevation setting?

    Well it is basically kind of like this. If you want everything on SPC we can do that and we do when requested, or on those jobs that require it. We also charge appropriately, which we have some clients that don't want something they don't need.
    also have a question if you require everything in SPC, is that in grid or ground ?

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    Default Re: Best Practice for search coordinate export: elevation setting?

    Quote Originally Posted by cadtag View Post
    So, you're creating maps that you know up front are based on invalid information, and generate bogus data? Dunno about losing sleep, but losing jobs? That seems likely.

    Anyone who provides me with a survey that is NOT on state plane, and uses bogus elevation data, does NOT get hired again.
    @CadTaG

    This is actually normal practice to send field crews out to do recon for establishing property lines. Its easier to send them out with a point in the general area of where a monument or pin should be located based off of filed maps and deeds. This helps out alot on large tracts of land, where there might be a pin in the middle of a huge field. The survey crew will go and shot the point either using GPS or the office guys will then move the points in the field to the correct coordinates, either SPCS or deed based depending on the project. Not all projects need to be in SPCS and some should stay in Deed base.

    @quarters

    Doing field recon, i never set any elevations for the points that are exported. They are just trying to find control horizontally. Once that is found then they can make those adjustments in the field or can be established in the office.

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    Default Re: Best Practice for search coordinate export: elevation setting?

    Quote Originally Posted by cadtag View Post
    Well, maybe that's a valid rationale for creating maps with deliberately bad data, but that's doesn't mean I have to like it. Crud creeps, and GIGO is pretty much a universal law of nature.
    Its not creating maps with bad data. You are simply locating control in the field so that the area you are surveying is in the right spot and is with in the property lines defined.

    Sending field crews out blindly to locate control on a site could take days to do without any guidance. Creating a point file indicating the Norhting/Easting - Lat/Long of certain areas of interest that could possible contain control so that a parcel of land can be correctly identified and located is alot faster.

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    Default Re: Best Practice for search coordinate export: elevation setting?

    Quote Originally Posted by remi678731 View Post
    Well it is basically kind of like this. If you want everything on SPC we can do that and we do when requested, or on those jobs that require it. We also charge appropriately, which we have some clients that don't want something they don't need.
    also have a question if you require everything in SPC, is that in grid or ground ?
    Grid. There's invariably some GIS data I need, and any survey info I get that can't be tied to SPCS is pretty much of (very) limited utility.

    And it really doesn't matter what the _original_ purpose of the drawing was, inevitably the purpose will morph and expand as the data gets used and reused.

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    Default Re: Best Practice for search coordinate export: elevation setting?

    Quote Originally Posted by cadtag View Post
    Grid. There's invariably some GIS data I need, and any survey info I get that can't be tied to SPCS is pretty much of (very) limited utility.

    And it really doesn't matter what the _original_ purpose of the drawing was, inevitably the purpose will morph and expand as the data gets used and reused.
    That is your work flow. It doesn't necessarily work for everyone. We do several different types of projects for different reasons. We use assumed coordinates, SPC, CORS, etc depending on the project and requirements. A word of caution with SPC we received a project to stake. The client designed a large wharehouse in a dwg on SPC in grid. The problem they didn't understand the difference between grid and ground.

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