Tag Archives: PM800

Drinking the NovAtel OEM 6 Kool-Aid

I have tested the NovAtel OEM 5 boards in several receivers (Viva, Carlson Surveyor GPS, X900) and while they have been okay in a matched base – rover pairs, they have not compared well to systems based on the Trimble BD970 boards or Spectra/Ashtech ProMark 800 receivers.

A week ago, I had an opportunity to compare a BD970 based receiver with a receiver using the NovAtel OEM 6 board under the big tree in front of our office. (I will describe the test I run in a moment.) Both receivers use exactly the same antenna element (in fact they are nearly identical.)

The OEM 6 is simply amazing. Solutions are really snappy. The ‘verified fix’ usually happens a few seconds after the initial fix. [For some reason, I find myself liking the dual fixing quite a bit. Especially when the verified fix happens so quickly. The OEM 6 really feels good under canopy.]

Here is a quick description of the test I run:

1. Corrections are served by the TURN VRS network in RTCM3 format with a virtual base 1-mile to the north. The corrections are played through a Pacific Crest UHF radio so that both GPS receivers under test get corrections at EXACTLY the same time.

2. I use two prism poles, 1 meter apart. The left pole is 1/2 meter lower than the right pole.

3. I wait for both receivers to fix, count to 5, store a single position, then dump both receivers, exchange positions and repeat. 60 times. So I have 30 occupations for each receiver on each pole. (I wait 5 seconds after the receiver fixes, independent of the other receiver.) If a receiver won’t fix in two minutes, I move it away from the tree, then sneak it back onto the pole.

The test location is, well, horrible. There is a giant tree 2-meters to the South, a two-story building 2-meters to the East, and big power lines to the west. The location is not suitable for GPS work. Which makes it perfect for testing receivers.

In the past, the OEM 5 boards have not fared so well in the Trimble VRS network. (The Trimble BD970 is matched to the Trimble VRS network and usually beats out every other receiver that I have tested other than the PM800 which either as good or better.)

But the OEM 6 has as good of performance as the BD970 based receiver. Absolutely.

What makes this remarkable and noteworthy is: the OEM 6 is about $1,200 less when bundled into a rover solution. Thats $2,400 for a base-rover pair.

Your takeaway should be: “Consider OEM6 based RTK GPS receivers. They are hot. Much better than the OEM 5 based receivers.”

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MiFi vs. Sim Card

Last October I buried comments about MiFi vs. Sim Cards in a post about Using a Z-Max receiver with a network connection.

Well, a week ago I purchased a used ATT MiFi device on eBay (AT&T Sierra Wireless Aircard 754S Elevate 4G LTE Mobile Hotspot Modem Router) and had a (wait for this) FANTASTIC experience.

I bought a used MiFi device because I did not want to encumber my #1 sim card (I have two) with a contract. The device was shipped within an hour and it worked perfectly when I received it. But it would not log onto the local ATT network.

So I called ATT described what I wanted to do and was immediately escalated up a level to an amazing support guy. He made the back-end changes to the card’s registration and the MiFi worked (they just added LTE in Salt Lake so the speed at my house hovers around 20 Meg download which is 10 times faster than the DSL. The card is good for 5 GB of download, you probably only need 200 Meg if you are only going to survey.

When I made the change, I was positive that the card would no longer work in the SP/Ashtech devices. However everything I have tried so far (PM100, PM120, PM220, PM500, PM700, PM800, LT30, MM10) has worked just like before.

[I want to reiterate that the ATT Tech Support guy (who I probably should not name, but will) Aarron Lequia was simply-absolutely-amazing. He made the changes and then patiently waited for me to try the card in a 1/2 dozen devices, just in case I wanted to revert back to the old configuration. The customer support at ATT could not have been any better.]

Now, back on topic:

Advantages of Using Mi-Fi to Data Collector Method

  1. You can see the status of your internet connection on the Mi-Fi screen:
    With a glance, you know your MiFi device is online.
  2. The Wi-Fi connection from a Surveyor+ to the MiFi is bullet-proof. It just happens and works every time.
  3. You can get a Mi-Fi device from Verizon for use where ATT and TMobile have no service!
  4. Typically the price for a Mi-Fi subscription is lower than a sim card. And because no phone service is associated with the Mi-Fi, there is no tax on the service.
  5. You can use the Mi-Fi with other devices (tablet, laptop, multiple rovers), leveraging the internet service investment.
  6. The data rate connection is way faster with the MiFi. In the case of a PM220, it appears to be 100 times faster. If you are using Dropbox to move DXF files, this could be a big deal.
  7. My cell phone does ‘data roaming’ in South West Wyoming. But my MiFi does not (I do not understand why.) So my MiFi gets unlimited roaming data but my phone does not. By connecting my phone to the MiFi I can minimize my roaming data.
  8. There does not appear to be any tax appended to the MiFi bill. (But holy cow, there are plenty of taxes added to my cell phone bill.)
  9. We install a small tool that allows us to remotely control the screen and keyboard on your data collector. If your phone does not support  simultaneous voice and hotspot, then we can’t talk to you while we fix your receiver.

Disadvantages of Using a MiFi

  1. Plan costs a bit more per month.
  2. On the PM120,220,100,200 and MM120,100 you have to have a WiFi card in the side of the unit.

Disadvantages of Using a SIM Card in a Rover’s Internal Modem

  1. Once you make a connection, you can’t read the signal strength on any of the devices I sell. The signal strength from before the data connection is shown, not the current signal strength.
  2. Entering all the passwords, user names, server names is a pain in the butt. (This is now mitigated as I just leave everything blank and it works the first time.)
  3. The data collector and GPS internal modems do not support 3G and 4G connections.
  4. The card can only be used with one device, unless you remove it which is difficult.

Interesting Complaint with MiFi

One note on MiFi. I have heard complaints from others that their data collectors will disconnect WiFi from their MiFi while they walk or drive around a neighborhood.

The problem is: they have to ‘reconnect’ to the network when their data collector moves between networks.

I have never personally seen this and I believe it to be a bad configuration in the data collector. The setting is “Automatically Connect to Open Networks”. Obviously it should be ‘unchecked.’


So, if you’re thinking about provisioning data service to get network corrections, I still recommend a MiFi device.

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New ProMark 800 Firmware V1.6 Released

New ProMark 800 firmware was placed on the ftp site yesterday (May 21st, 2013).

You can read more about the change here [ Info ]

You can download the installation file here [ V1.6.S812Ku26.tar.bz2 ]

The firmware enhances Z-Blade performance under ‘difficult’ (think canopy) conditions; adds QZSS tracking and improves TTFF (Time To First Fix) performance with VRS systems.

I have loaded this new version and I am going to admit that the changes are subtle. Not because they are not there, but because the PM800 had such high performance with the previous version.

If you have not tried a PM800 under canopy yet, you should get your local dealer to run out and give you a demo. The PM800 is just amazing: the performance when traversing under heavy canopy would have been unthinkable a year ago.

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