Land Surveyor Community Forum

Traverse without bearings

Hi

I'm responsible for the design and construction of UNHCR's refugee camps in Jordan for Syrian refugees. Amongst my jobs I make rapid assessments of sites for suitabililty. I'm an engineer by profession and lack the specialist knowledge of trained surveyors and have come here for advice.

I assess prospective sites by travelling the perimeter by foot or car with a handheld gps and uploading the track to a pc. However not all sites allow me to reach the perimeter. For these I'd like to be able to carry out a traverse from selected points for which I record gps coordinates. To do this I plan to obtain a laser rangefinder able to range out to 1000 metres or 1500 metres. I could then use a handheld compass to take bearings to each point.

As the compass accuracy is no better than three or four degrees an alternatrive is to use just the rangefinder data. My questions for the experience surveyors here:

1. Is it possible to carry out a traverse using just distances and not distances and bearings? Shots to each point from more than one station would be made resulting in good redundancy. I'd need some program to make adjustment for closure.

2. Are there traverse programs that permit different weightings for distances and for bearings? When calculating adjustments I could then assign priority to the more accurate distances and give minimal priority to bearings which are of low accuracy

3. Can anyone recommend suitable laser rangefinders? They need to be handheld as a tripod would not allow me to travel as light and as fast as I need to.

Thanks in advance for your contributions.

Robert

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Replies

  • This is a very interesting discussion for many reasons.  Here are some of my observations:

    1.   Every mathematical model of geospatial relationships among and between objects in the model are not the true objects, themselves, but an approximation of the location of the objects in space and time.

    2.   The are no necessary "expected results"; only an interpretation of the factual evidence of the model,  which may dangerously tend to become a future method of constraint in a model of interpretation for similarly categorized experiences.

    3.   "Similarly categorized" means the following:  Cataloged in the human mind as belonging to the same set of circumatances.

    4.   A set of circumstances in and for creating a geospatial mathematical model are inherently unique; thus not a matter of duplication.

    5.   The only method of arriving at an acceptable solution to an unique problem will tend to involve creative and intuitive thought, and will likely become the topic of discussion among others facing an unique set of circumstances.

    Scott D. Warner, R.L.S.

    Senior Director / Editor

    Land Surveyors United

       

    • Umm.......yes.

      Robert

      • Hi Robert... In my opinion, If that activity is only for ASSESSMENT and requires only rough position/ Location, your Laser Tech Industries TP360B laser rangefinder is capable of triangulation or trilateration as mentioned by Paul above, your rangefinder can even provide you missing line. 

        However, if the survey will be used for Approval of Fixed Points, basically, boundary survey and demarcation shall be carried out by a qualified surveyor where for such big Area as I'm assuming, a Geodetic Survey is necessary. Also, In such case, shall refer to Land Surveying Rules and Regulations of that area or other laws or rules of the same purpose.

        I hope you can pick a piece in my lines... Good luck...

  • Hello, I dont know if this will do the job for you. .  but you can try to look for Mapsmart program that comes with the laser range finder. . I think its truepulse laser range finder. . 

    But Im not sure if you can do like 1000 meters. .  as I understand its can do 800 meters. . and you can adjust and close your traverse. . 

    Hope this may help you. . 

    • Thanks for the suggestion. I'm not familiar with Mapsmart. It didn't come with the Trupulse; I'm told by the importers that it's an extra-cost option.

      As far as range is concerned, I find it's very dependent on target quality. A staffman in a white shirtt gives me 800 meters without trouble which is as much as I need for now.

      thanks again

      Robert

      • Well Im sorry, yes indeed its an extra cost to the range finder.

        I dont really know if they have video of mapsmart.

        you ca try to browse from the net.  

        here some of its capability;Field data collection and mapping software by LTI for the non-surveyor. Measure stockpile volume, distance, height, azimuth, position, area and elevation

  • Hello Robert,

    I understand your position but am concerned with the accuracy you want to attain for your survey. Early geodetic surveys were constructed and supported by frameworks of triangles...

    trilateration


    (Mathematics & Measurements / Surveying) a method of surveying in which a whole area is divided into triangles, the sides of which are measured, usually by electromagnetic distance measuring for geodetic control or by chain survey for a detailed survey...
    Using distance only, you would have to set a base line between two known points, set two monuments as accurate as possible square to your projected site, say 100 feet apart, from that baseline you could develop triangles, 3x4x5 in any proportion necessary, setting monuments as you go, your check is by measuring the hypotenuse or the diagonals between your set monuments.....just basic thoughts...need to think more on the subject...will get back to you....yes there are closures that consider angles or distances or weigh both the same...but for what your doing you may want to look at this attachment....again this is just rough ideas at this point.... Paul
    • Thanks Paul, That's a very valid point you make. And  thanks for the helpful text. I omitted to explain the purpose to which I hope to apply traversing by distance.
      I design and build refugee camps for UNHCR. Part of my work involves rapid assessment of sites as to suitablility. This has to be done with handheld instruments as the work environment does not permit tripods. I work alone and security considerations militate against anything that looks vaguely official or military related.

      I have a Laser Tech Industries TP360B laser rangefinder that measures  out past 1000m reflectorless. I need no more than +/- 1m for each shot so a misclosure of several metres will not bother me. The rangefinder also gives azimuth so I could use that and carry out a conventional traverse, though azimuth accuracy is only 15 minutes.

      I'd like to have the option of using distance and azimuth or just distance. Is this possible?

      Thanks again for your time

      regards

      Robert

      • Hello Robert, given the constraints, accuracy ability of your instruments and lack of necessary foundation for your instruments I believe that distance only is your best bet. Solve the triangles distance only. You could use azimuth as well but treat it as a separate survey.This may give you a relative check by comparing areas. Your in a tight spot, but you wouldn't have taken a job like that if you did not know what you were up against...I admire your courage...if you can get repeatability from different locations which will allow you to keep track of your error as you mentioned I think you can build a framework of triangles. You really need some way of maintaining the integrity of the point your shooting from... your starting monuments in which you build from have to be reliable. Targets with plum bobs suspended from lath may not present an obvious threat, natural (land marks)foresights and backsights may help....do you have utm maps of the area? Sorry I could not be of more help...will continue to ponder....Paul

      • Your device is already capable of this work.  Store multiple observations from separate points and mean the resulting coordinates.  Using a staff or monopod will enhance your accuracy.

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