Monthly Archives: January 2017

Wow, there has been a lot of ink spilt on North Arrows and projection declarations for jobs based on GPS data.

Since I am not a licensed surveyor, my opinion does not count. But I get asked all the time. So here is an example of what I might do as a minimum:

I, Joe Blow, do hereby certify that I am a Professional Land Surveyor, holding 
certificate 99999 as prescribed by the State of Chaos.
I further certify that I have prepared the diagram represented herein and that
the same is an accurate representation of a survey, and was conducted under
my direct supervision.

Benchmark
  The Benchmark for this project is CP201

Coordinate System and Projection Information
  Horizontal Datum = NAD83, North American Datum 1983,
                     2011 Realization 2010.0 Epoch
  GPS Control = Maine DOT Virtual Reference System (VRS)
  Vertical Datum = NAVD88, North American Vertical Datum of 1988, 
                   GPS Derived
  GEOID (used for GPS Derived Heights) = GEOID12B (NGS)
  Ellipsoid = GRS1980
  Projection = Maine West NAD83 State Plane Coordinates 
  Distance = US Survey Feet (1 Meter = 3937/1200 US Survey Feet)

Distances
  Distances are Grid distances converted to Ground using a Combined Scale Factor
  The Combined Scale Factor (0.99996067) for this project was derived at
    Control Point 201
          CP201 = 44 2 55.34000 N 69 58 23.05000 W NAD83
          Ellipsoid Height 215.562 ft
          GEOID            -57.100 ft
          Ortho Height     272.662 ft [NAVD88 (Computed using GEOID12B)]

    Example: 9,857.824 SFeet Grid = 9,858.206 SFeet Ground

Bearings
    Bearings are with respect to State Plane Grid North
    Declination at
       TN-SP  0°  8’  4.57”
       TN-MN 15° 36’ 37” (2017 Estimate)

{My Seal}
Joe Blow
Chaos PLS Number 99999

Let’s assume that we have an .RW5 (Raw File) for a job in one projection (a custom projection) and we want to reuse ‘SOME’ of the coordinates and GPS shots in this job, in a completely NEW job with an alternate projection.

Thesis: I have hundreds of control points and boundary shots for a job that were taken in a custom LDP. Now I want to work on an adjoining site, but in a new projection (or perhaps a standard State Plane Projection.)

If we assign the previous file as the control file of new job with a completely different projection, then we can import the RAW GPS positions to set a base, and we can use the raw data as the GPS coordinates for a localization.

Continue Reading > survce_reusingcoordintesbetweendifferentjobswithdifferentprojections_reva

The SP80 is billed as ‘the most connected receiver’ and without question, it is.

The internal Wi-Fi transmitter makes it possible to connect a SP80 directly to a Mi-Fi, which reduces the amount of data on the Bluetooth channel.

Let’s look at a comparison between the traditional ‘Data Collector Internet’ (DCI) configuration vs. the SP80 method  [ … sp80-survce_wifi_connection … ]