Setting Up a Base with Local Coordinates

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“Okay, I understand that I MUST set my base to a geodetic location that is within 200 meters of my base’s TRUE geodetic location X, Y and Z. But I still want to set the base at a known position and I don’t have a transformation. I swear I can do this in other software packages!”

You can do it in SurvCE also. Here is how.

First go to “Equip: 6 Localization: GPS (tab)”. Set the One Point Azimuth to ‘Geodetic’ or ‘State Plane Grid’ as desired. If you are going to use a system like 1000,1000,0 then you probably want to pick ‘Geodetic’. If you are going to use a state plane or modified state plane coordinate then you undoubtedly want to select ‘State Plane Grid’:

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Also check to make sure that an appropriate Geoid File is specified. Even if you are in Latin America and have a crappy Geoid file, you STILL need to select it or your elevation error will increase as you move away from the base.

Click on the green check mark to return to the Equip tab.

Do the standard base configuration steps: “Equip: GPS Base: setup Current, COMS, Receiver and RTK tab normally”. Click the Green Checkmark in the upper right corner.

The ‘Base Configuration’ tab is shown. Select the “From Known Position” tab:

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In my case I want to enter local coordinates 1000, 1000, 0; so I click on the center button ‘Use Local Coordinates’:

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Enter your desired coordinates, then click on the green check mark. SurvCE will ask you what you want to use for the localization file. The default is the job name with a .LOC extension:

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Accept or modify the filename, then click on the green check mark.

SurvCE will read an autonomous position from the base. (In the USA this position will be within a couple feet of the IGS08 current epoch true position; elsewhere it will be within 5 meters.)

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Click on ‘Yes’ to continue.

The base will be configured and SurvCE will ask if you want to store a reference file:

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Click on ‘Yes’

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Choose an appropriate name and click on the green check mark.

Your base is now broadcasting corrections and if you could occupy the Base Point (under the base) with your rover, the rover would read ‘1000.00, 1000.00, 0.00’ as you desired.

You are ready to survey, but let’s spend a few extra minutes and address two things:

  • what is going on in the background?
  • how do I setup on this same base point the following day?
  • what if I have more than one rover?

What is Happening in the Background?

First off, SurvCE has done a ‘Read GPS’ and used the autonomous location to initialize the base. The base does not think that it is at 1000, 1000, 0; the base thinks it is at a position that is very close to it’s TRUE position:

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SurvCE automatically sets up a single point localization. You can view it by going to “Equip: Localization: Points”:

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Notice that the control point’s local coordinates are the point  that I manually entered. Click on the ‘View’ button:

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and the corresponding geodetic position is the autonomous (WAAS corrected) base point. This base point is also saved in the .REF file.

So to recap, SurvCE has initialized the base with a ‘Read GPS’ position and then automatically configured a single point localization that results in the base reading the exact local coordinates that I requested.

How do I setup on the Same Base Point on a Following Day?

You want to use the .REF file to insure that the base is initialized with the exact same geodetic position that was used on the first day.

Setup the base over the EXACT same X-Y location as the first day. The HI does not need to match. Enter the correct HI on the ‘Receiver’ tab:

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When you click on the green check mark, you will go to ‘Base Configuration’ dialog. Select the ‘From Known Position’ tab:

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Click on the ‘Read From File’ button at the bottom:

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Select the same reference file that you saved on the first day, then click the green check mark.

SurvCE will check to insure that the broadcast geodetic location is close to the actual location, then display the position read from the file:

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Click on Yes:

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And the base is reconfigured exactly as it was the first day. Since you are still using the original job file, the correct localization is automatically used. You are good to survey!

What if I have Multiple Rovers on my Job?

Then you must move the localization file (.LOC) onto each of the other rovers and load it with the load button in ‘Equip: Localization: Points (tab)’:

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Then select the .LOC which you moved from the first rover data collector:

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Again, the second rover is now ‘registered’ with the same localization and will follow the first rover’s coordinates exactly.

3 Comments

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3 responses to “Setting Up a Base with Local Coordinates

  1. Pingback: Setting up a Base in Carlson SurvCE | ashgps

  2. I don’t kniow where i can ask this question.
    Don’t be angry this.
    I have two GPS Promak 2. They have problem with displey. I need two new displeys for gps.
    There are no any information on display about his model.
    Maybe you have technical documentation for Promark 2?
    Maybe you have name (code, type, anything) about displey of Promark 2?

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