Symbol used for representing recorded GPS Features

A customer reported that he had collected a number of points using iCMTGIS Pro and Arrow 100. Although the Topic in his Feature List have specific symbols assigned to them, the recorded points were displayed using the default blue dot symbol.

We have determined that this is a software bug in some of our apps. We will work on fixing this issue. In the mean time, you can click the “Pattern” button to select the desired symbol before storing data.

Which coordinate system should I use to collect GPS data?

“Is this the standard configuration ( WGS 84 LLA ) in iCMTGIS pro? Will it transfer back and forth in different coordinates? Or should I collect data also in NC State Plane since shapefiles are NC SP?”

Internally our software stores location data in WGS 84(1674)/ITRF08.

The options under Setup – Coordinate system is for you to select the coordinate system for displaying the position data.

Many people use the WGS 84(1674)/ITRF08 system on the iCMTGIS PRO because they are familiar with it.

You can set the iCMTGIS PRO to NC State Plane to collect GPS data if you wish to see the coordinates displayed in that system.

The important thing to remember is that when you are combining data (such as by importing Shapefiles), you must make sure that they are in the same coordinate system. You cannot add apples to oranges and expect to get a sum that represents the total number of oranges. In many cases you don’t have the option to change the coordinate system of the Shapefiles at their source. Therefore, our iCMTGIS PRO and PC software provides the ability to switch to the coordinate system used by the Shaepfiles to be imported.

Some people also use geo-referenced images in .tif format. Here again, you will need to find out what coordinate system the .tif file refers to before trying to load it into our software.

For people who make use of data from a RTK network, the Datum must be set to match that used by the RTK base station.

How to record points for contouring an area using iCMTGIS PRO

“I went to GPS > Collect, but I might have collected a line after that, rather than a traverse. Would that still be usable to generate contours?”

1. You can disconnect a Line Feature into Point Features by selecting that Line then using Utilities > Disconnect. Each node of a Line Feature is just one GPS fix. It may not be that accurate.

2. GPS > Collect > Traverse > Store will let you select a reference (starting Point) then enter slope distance, slope angle and bearing to create a new Point. You could generate new points this way when GPS signals are weak.

3. To properly record points for contouring, you will want to use GPS > Collect and record each point for a session of at least 30 seconds to obtain an averaged position. Generally, a longer session time results in better accuracy.

4. One thing to keep in mind is that vertical distance accuracy of GPS receivers is generally 3 times worse than horizontal distance accuracy.

How to record GPS points using iCMTGIS PRO and Arrow 100

“We are focusing in how to collect data points to create a block then a series of blocks to create a ranch then transfer to software to make a ranch map. Can you help us understand it better?”

Here are the steps for recording GPS data using iCMTGIS PRO and the Arrow 100.

1. Pair your Arrow 100 with your iPad via Bluetooth.

2. Start iCMTGI SPRO and create a Job file by tapping the Main Menu icon then selecting Job – New Job. Enter the new Job name. If you are using a Feature List for collecting the Points, please select it for the Job.

3. In iCMTGIS PRO tap the Main Menu icon then select Setup. Select GPS then tap on the check box for Enable the external GPS. Select the Arrow Device then tap on the green check mark at the top to confirm.

4. Tap on the GPS icon then select Turn External GPS On. You should hear the navigation beeps.

5. Select GPS – Collect.

6. Tap on New then select (if Feature List is used) or enter the Feature Name. As you would like to collect Points then use them to create Areas, please select Point and Static. Enter the Time Session in seconds then tap the green check mark to confirm.

7. If you are using a Feature List, the Attributes will be displayed, and you can enter the Values. Stand still and tap the Store button to start recording GPS position. You should hear the featuring beeps.

8. Walk to the next point and tap Store again. When done collecting all the Points, tap on the Exit button.

9. To create the Area Blocks, first create an Area Feature called Block by using Topic Menu – New Topic. Select Area as the type of the Feature. Then, select the Tools Menu and use Add Area manually to join the points to form the Area Feature.

10. As you have the PC-GIS X software, you could simply transfer the .pmp Job file to PC-GIS X after collecting the Points. Then use PC-GIS X to form the Area Features.

 

iCMTGIS PRO for soil & water application

Navigating back to a GPS point

“I am trying to find the right app for my application. What I need to do is use my iPad and Eos Arrow 100 GNSS receiver to collect and precisely navigate back to points on the ground. Getting back to the point with the subfoot precision my equipment is capable of has proven difficult with other apps because so many are based on my location being indicated by a large blue dot on an aerial photo or map. I need more precise navigation.”

As you can see from the Point Stakeout screen, there is a tiny green dot within the GPS marker to indicate the exact point location. When you get close to the target, you could turn off the Map.

For precise RTK surveying, users usually get the iCMTGIS PRO, which can get the GPS messages directly from the Arrow receiver and not have the data truncated by iOS. iCMTGIS PRO also provides many additional functions that you will find useful for your soil and water applications.

App to help plant trees?

“I am wondering if any of your programs could be used in my tractor as a way to guide me in driving a straight line when planting Christmas trees? Even if it doesn’t help me row by row could it be used to help me lay out a planting? Help to drive the first line across a field?”

The GPS system you will need to guide a tractor along a line to plant Christmas trees requires a high-precision GPS receiver used in conjunction with an app that will let you record a few reference points, draw the line on the map and guide the tractor along the line.

The actual equipment and app you select will depend on the accuracy you wish to achieve. Of course, a high-accuracy system comes with a high cost.

The SXBlue Platinum and EOS Arrow Gold GPS receivers can be used with iCMTGIS III to achieve sub-meter accuracy.

The SXBlue Platinum and EOS Arrow Gold GPS receivers can be used with iCMTGIS PRO and a RTK network to achieve cm-level accuracy.

As there will also be visual cues to guide the tractor, do you think sub-meter accuracy will be sufficient for you?

Both iCMTGIS III and iCMTGIS PRO will let you load a geo-referenced background map (*.tif. *.pim or *.bmp). These are useful as a general reference, but they are not accurate enough to let you pin-point your first point or line by digitization.

You could use iCMTGIS III with a SXBlue Platinum or an EOS Arrow Gold GPS receiver to record the property boundary and the starting point to sub-meter accuracy. iCMTGIS III and iCMTGIS PRO will let you create a grid over the property to indicate where the trees are to be planted.

iCMTGIS III and iCMTGIS PRO provide the Stakeout functions to guide you along the grid lines. These apps will display how far the tractor deviates from the line. You could also set up the apps to keep beeping as long as the tractor stays on the line within the specified tolerance.

Recording property lines

“I have recently purchased a 19 acre field/forest and have a new survey PLAT with freshly marked property pins. I would like to permanently record the data points onto a GPS device such as an iPhone for when the markers are removed (to install fences, argue with neighbors over hunting areas, etc.). I need the app to be able to guide me between the pins while walking with the GPS.”

For your intended use, you will need a high-precision GPS receiver. The GPS built into the iPhone is good to about 30 ft or worse in some situations. This is in adequate for settling arguments between neighbors.

The Deed Calls and Deed Calls & Stakeout apps are for drawing the deed plot by entering the deed calls (bearing and distance information). The Deed Calls & Stakeout app will then be able to guide you along this deed plot. To correctly place the plot on the map on the iPhone, you will need to have the GPS coordinates for the first point. These two apps do provide a “Pick GPS” button for you to grab one GPS fix. However, it will be an approximate position if you are just using the iPhone built-in GPS.

As you want to record the positions of the stake points and also be guided to walk between the pins, the system to use is a high-precision GPS receiver like the iSXBlue II+ GNSS or the EOS Arrow Gold with an iPhone or iPad running iCMTGIS III or iCMTGIS PRO. The iCMTGIS III and iCMTGIS PRO apps will let you record a position by taking many GPS fixes and averaging them. They will also let you record an irregular property boundary by walking along the boundary. They provide the Point Stakeout (to guide you to the pins later) and Line Stakeout functions (for guiding you along the property boundary later). They also provide the Deed Calls functionality.

In summary, it boils down to the desired accuracy. Using an iPhone running Deed Calls or Deed Calls & Stakeout app might be adequate for a realtor or a forester (to do a quick approximate deed plot). Deed Calls & Stakeout is useful for someone who needs to find old stakes based on a deed plot. To record accurate stake positions, you will definitely need a much better GPS than the iPhone GPS. If you can accept a 2 m – 5 m (6 ft – 15 ft) error, then you could consider using the less expensive Dual XGPS-150A or Bad Elf GPS.