Does the Arrow 100 work with iCMTGIS III or only with iCMTGIS PRO?

The Arrow series GPS receivers work with both the iCMTGIS III and the iCMTGIS PRO.

iCMTGIS III gets the position from the iOS CoreLocation, to which the GPS receiver sends the location information. As CoreLocation truncates the data, accuracy is compromised.

iCMTGIS PRO has all the functionality of iCMTGIS III plus the ability to receive and parse the NMEA message stream directly from the Arrow GPS. iCMTGIS PRO provides the “Enable the External GPS” mode to interface directly with the Arrow GPS receiver. In this mode, the app can display a GPS status bar in real time. It will also let you set a limit on PDOP and RMS to help ensure data quality.


I was wondering if it is possible to use the gps receiver built in to an iPad with the iCMTGIS Pro program?

Yes, you can use the GPS receiver built into an iPad with the iCMTGIS PRO app. Please keep in mind that the built-in GPS receiver of the iPad is not quite accurate. If you just want to record a rough position or to have the app lead you to the vicinity of a location to find a stake, that is fine. In that case, you could just as well use a lower-priced app like the iCMTGIS III.

iCMTGIS PRO distinguishes itself by being able to interface directly with a couple compatible high-precision external GPS receivers to obtain accurate results. Some of our customers are using such a system in their RTK GPS applications.

Using iSXBlue II with iCMTGIS PRO

A customer using iSXBlue II GNSS with iCMTGIS PRO on an iPad mini 2 sent us a few question:

1) He wondered how to tell if the iPAD running iCMTGIS PRO is operating with the external SX Blue II.

With the iPad paired over Bluetooth with the iSXBlue II GNSS, tap on the GPS icon and select “Turn GPS on”. A GPS marker should appear and the app should issue a navigation beep once every second. This indicates that the app is receiving the GPS position data from the iPad, to which the iSXBlue II is sending the GPS signals.

Now, tap the GPS icon and select “Turn GPS off”. Select Main Menu – Setup then select GPS. In the GPS Setup screen, select “Enable the external GPS” then select “GNSS RECEIVER”. Set the threshold values as desired then tap on OK.

When you tap the GPS icon and select “Turn external GPS on”, a GPS status line should appear at the top of the screen, showing the number of satellites used, the PDOP value, etc. This indicates that the app is obtaining the GPS data directly from the external GPS/GNSS and not just getting the GPS position from the Apple CoreLocation.

2) With respect to the iSXBlue RTN NTRIP app, he asked, “I have this app and presume both your app and this one need to be open and running at the same time?”

RTK work means you are making use of the correction data sent out by a RTK network provider. Therefore, both the iSXBlue RTN NTRIP app and iCMTGIS PRO need to be open and running at the same time.

Using iCMTGIS PRO and EOS Arrow Gold to collect UAV ground control point data

“I have a UAV company and do lots of inspections and mapping with my drones, when I am doing the mapping in the past I have hired crews with total stations to get me my GCP’s so now I want to do this myself. I get the X, Y and Z data from them so I can input them into my Pix4D software. I know your software allows me to collect the X and Y data but can I also collect the Z data accurately?  . . . . .  Please see the attached GCP information sheet I get from survey companies. As long as I can get this data it will be great.”

These appear to be the coordinates for Point Features. So, you will want to first set up the coordinate system and distance unit to use. If you are using UTM, select the proper zone.

Now create a new Point Topic and give it a name, such as GCP (for ground control point). Then Edit the GCP Topic and add the built-in Attributes: Position_X, Position_Y and Elev_Z as well as the GCP ID attribute.

With the GCP Topic selected, turn on GPS and record a few points. After ending the point data collection, you can turn on Sheet View and look at the data in a spread-sheet arrangement.

You can export the point coordinates and attributes data to Shapefiles or a text file.

As the GCPs are control points, you will need to use the Arrow Gold GNSS receiver in RTK mode to get better accuracy.

Under Setup – GPS, select “Enable the External GPS” and select the protocol for the EOS GNSS receiver. This way, you will be able to see the RMS error of the GPS data output by the GNSS receiver displayed at the top of the Map View screen.

“Can’t open the session” in iCMTGIS PRO when used with EOS Arrow

“I went into Setup -> GPS, enabled the external GPS, chose Eos GNSS Receiver as the device and com.eos-gnss.positioning as the protocol. When I saved these settings and used the GPS menu to Turn External GPS On, iCMTGIS Pro gave me the error Cant open the Session.”

The correct protocol for EOR Arrow GPS receivers is:

The iOS device will automatically use the internal GPS if you turn on GPS within an app while no external GPS is connected. Therefore, you will want to have the external GPS connected first before selecting “Enable the External GPS” then tapping on “Turn External GPS on” under GPS.

Also, when any app is using the internal GPS, iOS cannot work with an external GPS connected to the device. Therefore, to make use of the connected external GPS, you will want to turn off GPS from all running GPS apps (including the one you are actively using) then turn on GPS within the app you are actively using.

If the “Can’t open the session” error has already occurred, you will want to close the app then restart it.

“OK that was it. I got a document from the company (reseller) that sold me the Arrow that instructed me to use the wrong protocol. I think at various times I was running into both this issue and the another application is using internal GPS issue, but now I know the correct sequence and everything appears to be working fine.”

Question about Forester GPSGIS II and Bad Elf Pro

” I have the program loaded on an Ipad Mini Retina with Cellular, Bluetooth and WiFi. My ‘ understanding ‘ is that this Ipad does, indeed, have a dedicated and ‘real’ GPS chipset. So far it has worked fairly well with the FORESTER II App. My question, is : IF I add a Bad Elf Pro ( hoping to get more accuracy) via bluetooth connection …… Will this affect the quality of the recorded tracks and points within the Forester GPS GIS II. “

Generally, connecting to the Bad Elf Pro should provide better accuracy for the recorded tracks and points within the Forester GPS GIS II.

With respect to how one can determine if the app is using the external GPS receiver in the app, please read the following blog post:

GNSS receivers compared

When considering the purchase of a high-precision/accuracy GPS system, we check the hardware and software capabilities and, of course, also look at our budget. The article at the following link covers the testing and comparison of a number of GNSS receiver contenders in the market.

If you click on “Data Capture” under “Test Methods”, you will see that the iCMTGIS PRO app was used in the comparative test of the various sub-meter GNSS receivers.

You can find the iCMTGIS PRO press release at the following sites: