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:



Will my GPS receiver work with your apps?

Here is an inquiry about using a specific external GPS setup with iCMTGIS III. “I am using NMEA-BT product from Aman Enterprise company. It is a external module for gps receivers (all gps receiver using NMEA protocol [i am using with Trimble R8]) connecting to iPad via bluetooth and also there is an iPad app bridging between iPad and GPS receiver also provided from Aman Enterprise Inc. So that it treats like built-in GPS receiver with high precision (using NTRIP protocol).”

If the GPS receiver is compatible with the iPad or iPhone device, then it should work with our apps, including the iCMTGIS III.

Now, there are different ways in which an app can work with an iOS compatible external GPS receiver. The basic way is for the GPS receiver to send position information to the iOS Core Location framework and for the app to grab such information from the Core Location framework. This is how our existing apps obtain the GPS position information from the Dual XGPS150, Bad Elf GPS, Garmin GLO, iSXBlue II and EOS Arrow GPS receivers.

Another way is for an app to get the NMEA output stream from the GPS receiver and parse it for the information that it will display. In this case, the app will be able to show the GPS position as well as additional information sent out by the GPS receiver, such as the PDOP, the status of the satellites and the position accuracy. The suppliers of the app and the GPS receiver must work together to make this happen. Currently we are in touch with a few GPS suppliers and trying to incorporate this External GPS functionality in a new app. This will take some time to accomplish.

Will iCMTGIS II & iGPSGIS II accept GPS signal from add-on GPS devices for the iPAD or iPhone?

This question was sent in as a comment. As it is a topic of general interest, we are posting it here. iCMTGIS II and iGPSGIS II use the Apple iOS standard API. We have not tested these apps with all the external GPS devices available for the iPAD and iPhone, but we expect them to work with a compatible GPS device such as the Dual XGPS150.

In fact, we have confirmed that iCMTGIS II and iGPSGIS II do accept GPS signal from the Dual XGPS150 GPS receiver paired with the iOS device. Our Deed Calls – Area – Perimeter app can also use this Bluetooth external GPS to set the point of beginning. 

Here is the link to a demo showing how to pair the Dual XGPS150 with an iPAD.