How can I make sure I’m capturing points meeting a PDOP threshold?

If you are using iCMTGIS PRO and an iSXBlue II or EOS Arrow GPS receiver, you can set the PDOP limit for GPS data collection as follows:

1. Turn off GPS from all apps on your iOS device.

2. Select Main Menu – Setup and mark the check box for “Enable the external GPS“.

3. Select the appropriate device protocol for the GPS receiver.

4. Tap on the pull-down arrow for PDOP Mask and select the desired PDOP Mask level. If you only want to record position data for which the elevation can be computed, then also mark the “3D Only” check box. Tap on OK to save the setting and close the screen.

5. Tap on the GPS icon then select “Turn external GPS on”.

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.

How to use iCMTGIS III to check GPS accuracy

“I have purchased the iCMTGIS III and I am using a TIFF image as a background map. I am having problems with the GPS not very close to a known point. Do you have any suggestions? I am using a Bad Elf Pro+ as an external GPS it says it is supposed to have 3-5 meter accuracy. Do you suggest another GPS? Is there only one place to change coordinate system or is there other parameters that may need to be changed to get acceptable accuracy?”

Does your iPad come with GPS? Perhaps the iPad is using its internal GPS, which has poor accuracy. Please turn off GPS from all the apps on your iPad. Then, with the Bad Elf Pro+ connected to your iPad and turned on, run iCMTGIS III and select GPS – Turn on GPS.

Another way to ensure that the iPad uses the external GPS is to turn on the Airplane mode under the iPad Settings. For details, please see our blog post at:

To check the accuracy of the GPS receiver against the LLA coordinates of a known point or survey mark, you could first create a Point Topic then add a Point by using the Add Point by Coordinates function from the Tools menu. Enter the latitude and longitude of the known point. With the Bad Elf GPS having been turned on for a few minutes, check the location of the GPS marker against the known point. The published accuracy is an average value.

To record a Point Feature, please use GPS – Collect and log GPS point data for 5 minutes or longer. The app will compute and display the average point position. Measure the distance between the recorded point and the known point.

Can I use iCMTGIS PRO on my iPad to stakeout to survey points and also develop custom data collection forms?

1. Stakeout to survey points

The GPS – Point Stakeout function in iCMTGIS PRO can take you to the survey points. How close you can get to the survey points depends on the GPS receiver. The built-in GPS of an iPad device has an accuracy of about 10 meters (sometimes better, sometimes worse). If there are markers on your survey points, then you could identify the marked points after you get to its vicinity. Otherwise, you will need a high-precision GPS receiver, such as the EOS Arrow or iSXBlue II GNSS to take you closer to the point position. To pin-point a previously surveyed point, you will need to connect the EOS Arrow 200 or iSXBlue II GNSS to a RTK network in your area.

2. Custom data collection forms

The GPS – Collect function will let you record Attribute values during data collection. You can use the GPS – Feature List function to set up the Features/Attributes/Values for your project. Similar projects can share the same Feature List.

GPS Feature Data Collection

GPS Feature Data Collection

You can set up custom value lists to facilitate data collection. During GPS data collection you can have the app display the Attribute fields. You can enter data manually or select the desired data from the pre-defined list. The collected data can later be presented in Sheet View and edited.

If you are not after entering data while recording GPS positions, but are interested in designing your own report forms for entering data for a certain site, then please consider our Wetland & Stakeout app.

Quick way to measure acreages using GPS

GPS Data Collection for Area Feature

                                      GPS Data Collection for Area Feature

“I currently have iCMTgisII on my ipad. I am looking for the simplest and quickest way to measure acreages using track points. what is the quickest way to achieve this using that program?”

You can use the GPS/Collect function to record an Area Feature while walking or driving along the perimeter of an area you wish to measure. The standard procedure is to first define a Feature List suitable for your project to facilitate data collection. However, if you just want to quickly map an area, you can use the following steps.

1. Tap on the GPS icon then select “Turn GPS ON“. Wait 5 – 10 minutes for it to stabilize..

2. Select GPS – Collect.

3. Tap on the “Area” tab.

4. Enter the Feature Topic Name, such as “area”. The app automatically assigns “area001” as the first Feature ID.

5. Tap on the Store button in the data collection panel then start walking. By default, one GPS fix will be recorded per second.

6. When you have walked around the area and come back to the starting point, tap the Stop button.

7. If you want to record another area, go to the start point for that area and tap on Store. The app will have assigned area002 as the Feature ID for this second area.

8. When done with the data collection, tap on the Exit button.

9. Back in the Map View, tap the Zoom-Fit icon to see all the areas in the screen. Tap on one of the areas to highlight it. Tap on the Feature Properties icon then tap on the “Length/Area” tab to see the perimeter and area values.

One thing to note is that the GPS on your iPAD is not quite accurate. It is probably fine for measuring very large acreages. For better accuracy (2-5 meters), many of our app users use a compatible external GPS receiver, such as the Dual XGPS-150A or the Bad Elf GPS. GPS receivers that provide sub-meter accuracy, such as the iSXBlue II and the EOS Arrow, have a higher price tag.

If I purchase iCMTGIS PRO for my iPhone, can I also install it on my iPad?

Some of our apps were designed specifically for the iPhone or specifically for the iPad, but iCMTGIS III and iCMTGIS PRO were designed for use on both the iPhone and the iPad devices.

You can install your purchase of this app on your iPhone and iPad devices as long as your devices use the same Apple ID.

A related question:

“If I get a new iPhone in the future, will I be able to re-download and install iCMTGIS Pro on my new device without having to purchase it again?”

Once you have purchased the iCMTGIS PRO app, you can install it in any new iPad or iPhone device that you purchase as long as the devices use the same Apple ID.

Please note that our iOS apps are sold via the Apple App Store, and all purchases and installations are governed by Apple.


How to recover custom configuration after updating iCMTGIS III

“I’ve been puzzled by question that whereas iCMTGIS iii keeps its settings every time we updated it, a few settings have gone to the default (for us: Elevation and Angle, and Data Collection). Can we have:
1) The configuration not touched during update (unless configuration parameters changed);
2) Float number for the Local Time Offset in Data Collection?
Otherwise, the iCMTGIS-iii has been working fine.”

The settings for Elevation and Angle and Data Collection are saved in the file named “cmtgis3.cfg“.

After setting up the desired parameters, you can copy cmtgis.cfg to your PC for safekeeping.

After a software update, the app must go back to the default system configuration, but you can restore your custom configuration.

To do so, please first run the app and open a Job so you will be able to access the app’s Documents folder.

Then close the app by double-clicking the Home button and then flicking the app screen upward and out of sight.

Now copy your custom cmtgis3.cfg back to the app’s Documents folder to overwrite the default configuration file. You should see your custom settings for Elevation and Angle and Data Collection.