Websites for some GPS receivers compatible with CMT iOS apps

Our iOS apps can work with any GPS receiver that is compatible with the Apple iPad and iPhone devices.

At the following three websites, you can find GIS-grade GPS receivers that claim 2 – 5 m accuracy:

https://gps.dualav.com/explore-by-product?category=GPS

https://bad-elf.com/pages/products

https://buy.garmin.com/en-US/US/p/645104

The Trimble R1 boasts 50 cm max. precision.

https://geospatial.trimble.com/products-and-solutions/trimble-r1

EOS and Geneq Inc. provide high-precision GNSS receivers.

Many of our customers are using the EOS Arrows series GNSS receivers with our iOS apps. In particular, iCMTGIS PRO can directly interface with the Arrow GNSS to obtain more accurate position data.
https://eos-gnss.com/product/

The SXBlue Platinum GNSS receivers from Geneq Inc. also work well with our iOS apps, and can directly interface with iCMTGIS PRO. Their SXPAD & SXPRO mobile data collectors can run our Windows Mobile 6.5 and WEHH Windows Embedded Handheld 6.5 compatible GPS/GIS data collection software programs.

https://sxbluegps.com/

GPS week rollover in 2019

It’s been 19.7 years since the last GPS week rollover took place in the year 1999. If you are still using an old GPS receiver for data collection, then after April 6, 2019 the GPS data will be recorded with a much earlier date. Newer GPS/GNSS use 13 bits instead of 10 bits to encode the GPS week value, and therefore will continue to work properly for a much longer time before the GPS week will be rolled back again.

According to EOS CTO Jean-yves Lauture, “GPS Week Number Rollovers have been accounted for and implemented in all Arrow firmware builds available from Eos since the creation of the Arrow Series™ product line.”

According to Donnay Fleury Nahimana, PhD, GNSS Development and Test Specialist, the SXblue devices of Geneq Inc. will continue to function properly after the 6th of April 2019 GPS rollover. The units are running GNSS firmware that accounts for the GPS rollovers on 13 bits since 1999.

According to John McLellan, C.H.ElF (Chief Helper Elf), Bad Elf, LLC, “I’ve been reassured by our engineers that rollover week is handled on all of our devices.” (4/7/19 update: We used our Bad Elf GPS-2200 to record a couple GPS points today. The date recorded is correct.”

According to the Dual Tech Support Team, “XGPS150 units that were manufactured before December 2011 will be affected by the rollover event. There will be a firmware version that will resolve this issue.” (4/6/19 update: We used our Dual XGPS-150A to record a couple GPS points today. The date recorded is correct.”

For Garmin aviation devices, please read the following article:
https://s23634.pcdn.co/en-US/aviationalerts/wp-content/uploads/2019/01/1905A.pdf

For Trimble GNSS units, please read:
https://community.trimble.com/thread/5699-are-trimble-gnss-receivers-ready-for-the-gps-week-2019

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:
https://icmtgis.wordpress.com/2014/03/05/using-an-external-gps-with-icmtgis-ii-on-ipad/

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.

Need app for lime spreading

“We are looking for a app that can assist us with our lime spreading operation……the app we are looking for would enable us to overlay a map with grid lines, these grid lines would ideally run North/South and East/West, and would need to be able to be adjusted/calibrated to suit the coverage width of our spreader, the app would then create a track that shows what areas we have covered.”

Our iCMTGIS III and iCMTGIS PRO for iPad and iPhone will let you directly load a GeoTiff file to use as a background map. These apps can also display the built-in Apple Map when wi-fi connection is available.

Farming GPSGIS II for iPad will display the built-in Apple Map via wi-fi connection. If you have PC-GIS X, you could use it to convert GeoTiff, MRSID and ECW map files to .pim files that can be used by Farming GPSGIS II as background maps.

You can use the above apps and a compatible GPS to record the perimeter of the area you will be working with. Or, if your farm boundary can be clearly viewed on the background map, you could digitize its perimeter. This will create an Area Feature. Then you can create grid lines over the Area Feature at the desired spacing in the North/South and East/West directions (or any other direction).

The above apps also provide a Line Stakeout function that can help the spreader stay on the grid lines.

With GPS turned on, you can use the app to create a track that shows where the spreader has been. This will be a Line Feature.

The important issue, however, is the desired accuracy. The GPS provided with iPhone and iPad devices are not accurate. Many of our customers purchase an external GPS receiver that is compatible with the iPhone and iPad devices. The Dual XGPS-150A and Bad Elf GPS claim 1-3 meter accuracy. iSXBlue and EOS Arrow GPS receivers can provide submeter accuracy, but they are pricey.

Questions about the Deed Calls & Stakeout app for iPhone and iPad

“I’m wondering if your Deed calls and stakeout app can be used to enter the deed calls in the office, then travel to the site to establish the starting point with the phone’s GPS? Also, do the deed calls have to entered directly into the app or can it import a text file? Finally, once the deed plot is established in the app, is there a way it can be imported and viewed in Google Earth.”

1. The Deed Calls & Stakeout app can help you stake out each node on the deed plot created by entering the deed calls in the office. iPhone’s GPS does not provide high accuracy. Some external Bluetooth GPS receivers, such as the Dual XGPS 150A, Garmin Glo and Bad Elf Pro claim 1-3 m accuracy. Higher accuracy ones like iSXBlue II GNSS and EOS Arrow are in the high price range.

2. Deed Calls & Stakeout can open a .dcf file. The deed calls you enter into the app are saved in a .dcf file, which is a text file that can be viewed and edited. Therefore, you can follow the same format to prepare a deed calls file for this app to open. Make sure the angle and distance unit settings in the app match those used by the deed calls.

3. Deed Calls & Stakeout does not provide KML export. It will export to DXF, which can be converted to KML. For details please see our blog article at this link.