Category Archives: GNSS Solutions

What to do for Absolute Antenna Calibrations, when there are not any?

I could write a book on the difference between relative and absolute antenna calibrations, but I don’t need to and you should not spend much time wondering about why. Or if. You ‘Just need to make the change to Absolute Antenna Calibrations’ for everything.

But, depending upon which antennas you own, you may find there is not an absolute calibration for your antenna! What to do?

First a little background. Let’s look at a couple of sample antenna:

Relative ASH111660       NONE L1 GPS/GLONASS, base of RF connector->N  NGS (  3) 10/06/02
       0.3      -0.7      75.4
Absolute ASH111660       NONE L1 GPS/GLONASS, base of RF connector->N  NGS (  3) 10/06/02
       0.9      -1.1      57.3
The Absolute calibration is -18.1 mm from the relative calibration.
Relative MAG105645       NONE L1/L2 GPS                                NGS (  2) 00/12/21
       0.6       3.6      65.6                              
Absolute MAG105645       NONE L1/L2 GPS                                NGS (  2) 00/12/21
       1.2       3.2      47.5
The Absolute calibration is -18.1 mm from the relative calibration.                   

In general, this trend continues for most antenna because they were NOT actually re-calibrated for absolute calibrations, the absolute values are 18.1 mm less than the relative values. This is because this is the difference between the reference AOAD/M_B Dorne Margolin B Chokering:

Relative AOAD/M_B        NONE Dorne Margolin B, chokerings (Rogue)     NGS (  0) 97/10/27
       0.0       0.0      78.0                              
   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0
   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0
       0.0       0.0      96.0                              
   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0
   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0
Absolute AOAD/M_B        NONE Dorne Margolin with chokerings (Rogue, A IGS (  0) 11/03/25
       0.6      -0.4      59.8                              
   0.0  -0.2  -0.9  -1.9  -3.2  -4.6  -6.0  -7.1  -7.9  -8.2
  -8.1  -7.4  -6.2  -4.6  -2.3   0.7   4.5   9.1  14.2
      -0.1      -0.6      88.3                              
   0.0  -0.1  -0.5  -1.1  -1.8  -2.6  -3.4  -4.2  -4.8  -5.2
  -5.3  -4.9  -4.0  -2.8  -1.3   0.5   2.8   5.7   9.4

The L1 difference (59.8 – 78.0) = -18.2 mm (sorry, I don’t know why it is 18.2 instead of 18.1)
The L2 difference (88.3 – 96.0) = -7.7 mm

So if you have an antenna like the NAP 100 with a relative calibration north : 1.0mm, east : 3.8mm, up : 73.2mm above ARP; which would look like this:

Relative MAGNAP100         NONE L1    GPS
       1.0     3.8      73.2

I believe it is safe to say the absolute calibration would be:

Absolute MAGNAP100         NONE L1    GPS
       1.0     3.8      55.1

By the way, if you are still using L1 only receivers to do static work (I will forgive you if you are running Stop and Go) you need to sell them (PM2, PM3) on ebay and trade-up to X90-OPUS receivers. The days of L1 only should be numbered!

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Filed under GNSS Solutions, PM3

Is a NGS CORS Station Available

Often I get the question, “what is up with CORS station ‘xxxx’. GNSS Solutions no longer will download data!?”

Here is how to find out if data is available from a particular site:

1. Browse to the NGS CORS mother site [ here ]

NGS CORS Page2. Type in the CORS site you are interested in checking out (I am going to look at SGU1):

ngscors2then press “Enter SiteID”

3. When the CORS Information page is displayed:

DataAvail

click on ‘Data Availability’.

4. Hang tight, it will take 15-seconds to display the profile:

DataAvail2Blue bars are good. Gray bars suck.

That is all you need to know!

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Nightmare on GIS Street: GNSS Accuracy, Datums and Geospatial Data

What is the difference between a reference frame, a datum and a realization?

Why is timestamping coordinates important?

What is the difference between NAD83 CORS96 and NAD83 2011?

Why don’t ESRI products support these concepts?

If you are like most people, it is all a nasty-ugly blur.

Wouldn’t it be great if someone make a simple video with really smart presenters that started to explain all of this?

Someone (Eric Gakstatter) did! And the video is great! It features Kevin Kelly the Geodesist from ESRI (who would have guessed that they had one?) Craig Greenwald and Michael Dennis from NGS who absolutely knocks it out of the park on this webinar.

This [ link ] should get you the webinar recording. You have until September 18th 2013 to watch it. Do It Now! I can not recommend this webinar highly enough! It is fantastic.

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Filed under Carlson, FAST Survey, GNSS Solutions

GNSS Solutions Version 3.80.4

The latest version of GNSS Solutions supporting PM120 and PM220 has been released.
Some of the items I am most excited about:
  Correctly imports jobs that earlier version broke into multipe occupations
  RINEX 3.01 support
  Updated Antenna Database (from NGS)
  Updated RGP and IGS Station Lists
  RINEX Convertor 4.2.1  Latest GEOIDS tool 1.1.0
  Fixed: ‘Land Survey Report’ failure under Vista and Win7
  Fixed: Partially imported Stop and Go files
  Fixed: Dynamic jobs errantly made from Static files
  Fixed: Antenna Heights not automatically set from imported files
  Fixed: Errant import of some Hatanaka compressed files
  Fixed: Antenna name not imported correctly on some files
  Fixed: GNSS Solutions won’t work on some Win7 computers
I have to tell you that a few of the fixed items have been making me crazy! This is a welcome release.
Information is available
  [ here ]
The folder containing the latest installation tools is
  [ here]
Because the tool is distributed as multiple files in an FTP folder, and will present problems for many users I have made a single ZIP file installation tool available:
  [ here: ZIPed Installer ] << Best link if you are inexperienced with FTP!

 

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GEOID 2012A for Ashtech GNSS Solutions and the GEOID Extract Tool

Update 11 Oct 2012: Checkout the self installer tool [ here ]

GEOID 2012A has been out for a month now.

I complied Ashtech Geoid .GEO files and have made them available for download.

http://www.alltopo.com/out/ashtech/G2012A/Geoid12A.zip

Decompress the ZIP file and then place the Geoid12A.geo file at this location (in Win7 64):

C:\Program Files (x86)\Common Files\Ashtech\Geoids

‘GNSS Solutions’ and the ‘Geoids’ extract tool will find the file the next time they are started.

If you are looking for GEOID12A for Carlson SurvCE, check out:

http://update.carlsonsw.com/kbase_main.php?action=display_topic&topic_id=843

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Filed under Carlson, FAST Survey, GNSS Solutions, Uncategorized

GNSS Solutions Version 3.50

GNSS Solutions Version 3.50

GNSS Solutions Version 3.50 has been released and is available on the Ashtech FTP site.
GNSS Solutions V3.50 ] < Single File Download
This is a major revision which provides support for the recently released
ProMark 100 and ProMark 200 receivers. Please refer to the ‘Release Notes’ link above for detailed update information.

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