Contour – Volume – Stakeout Questions

“My goal is to create an overview of my property and the complicated topographic conditions. Will I be able to create a map of my property with contour lines? Can I do that by importing a text file with hundreds of gps-position-altitude points? Is there another app might be more suitable for this purpose?”

If you have the boundary line of your property and a text file with 3-dimensional coordinates, the Contour – Volume – Stakeout app will be able to generate contour lines for the property. How good a representation you get will hinge on the resolution of the grid (number of points in relation to the length, width and height of the property) and the accuracy of the xyz coordinates.

If you have the Shapefiles for your property boundary, you can import it into the app to create the area representing the property. If your property boundary can be easily recognized on Apple Map, then you could use the app to digitize the property boundary.

Our iCMTGIS PRO app also includes the Contour-Volume function. It provides the function to use GPS to map property boundaries. The accuracy of the data depends on the accuracy of the GPS receiver. High-precision GPS receivers are quite expensive.

“So am I interpreting it properly .. I will not be able to register my property borders/shape with this app?”

The Contour – Volume – Stakeout app will let you get a GPS fix and compute a position when you use the Add Point manually function. You can then use the Add Area manually function to join those points to form an Area. However, the positions obtained this way are rather rough.

The GPS data collection function provided in the iCMTGIS PRO app will let you stand at a point and collect multiple GPS fixes to compute an averaged position. It will also let you walk along the boundary and record the boundary as a Line or Area Feature. Still, the accuracy hinges on the GPS receiver used, not the app. iCMTGIS PRO also provides the Deed Calls functionality to let you enter the property description in terms of distances and angles.

Question about Contour – Volume – Stakeout

“Does this app calculate the Contour and elevations based on Google satellite Aerials or do you need additional equipment in the field to be able to measure the different elevations?”

The Contour – Volume – Stakeout app will plot the contour based on the elevation data you enter or import. You will need to supply the elevation data.

Our iCMTGIS PRO app provides the GPS mapping and data collection functionality for recording 3D position data. You will need to use a compatible high-precision GPS receiver (such as the SXBlue Platinum or the EOS Arrow Gold) to obtain accurate results. iCMTGIS PRO also provides Contour-Volume functionality.

We do have software (e.g. PC-GPS 9, PC-MAPPER 9, CMT-Forester) for use on a Windows 7, 8 or 10 computer that will plot contours based on DEM (Digital Elevation Model) data provided by the NGS.

iPhone app for mapping property lines

“I just purchased the Stakeout ICMT app for my iphone. . . . I thought this was the app that worked with your iPhone GPS to walk the property line. But from your email it sounds like there is another one. What is the app called? Is there any way I can get a refund for this app and purchase the other one?”

Stakeout iCMT can help you approach an existing Point or walk along an existing Line or Area Feature in the Job file. It assumes you can import or digitize the Features to get their coordinates.

You could, if you wish, use the Add Area Manually function in Stakeout iCMT and log nodes for an Area Feature by tapping the PickGPS button once every few seconds while walking your property boundary. However, this is not how GPS mapping is usually accomplished.

Our iGPSGIS II app for iPhone provides the GPS mapping capability. While you walk around the property, you can have the app automatically log a GPS node every second.

Please note that the accuracy of your work will depend on the precision of the GPS receiver you use. The built-in GPS in iPhone is not that great (unofficially, around 10 meters). Some of our customers use the Dual XGPS-150 or the Bad Elf GPS 2200 to get 2-5 meter horizontal accuracy.

As these apps are sold via Apple, please contact Apple App Store to inquire about switching out an app that you purchased recently.

Really? You could use an iPod touch for GPS data collection?

Yes, provided you also get a compatible external GPS receiver to use with the iPod touch device. GPS receivers range widely in price, in keeping with the degree of precision they provide. A few expensive GPS receivers (such as iSXBlue and EOS Arrow) are available for renting for undertaking short-term work that requires sub-meter horizontal position accuracy.

Some companies employ multiple workers to perform GPS/GIS mapping and data collection tasks. Unless they already own iPhones, it will be more economical for them to run our iGPSGIS II or iCMTGIS III app on an iPod touch in conjunction with the external GPS receiver.


“I’m hesitant to spend $300 for the pro app if the $95 or $200 apps will suffice but I’m having a difficult time finding a comparison of features among the apps.”

Built-in Attributes 512x384

The three apps in the iCMTGIS-series all provide real-time GPS/GIS data collection and mapping functions. They will let you add user-defined Attributes for the recorded Features either manually or via a Feature List (attribute table). They will let you import and export Shapefiles. The differences are in the additional functionality provided by the more expensive apps.

If you just need to use GPS to map Points, Lines and Areas and record their associated descriptions, iCMTGIS II will do. iCMTGIS II can display the built-in Apple Map as background. If you would like to use an off-line geo-referenced background image, you will need to first use the optional PC-GIS software to convert the GeoTiff, GeoJpeg, ECW or MRSID files to the .pim file format. The .pim map can work in the “moving map” navigation mode. (Many of our existing customers already have the PC mapping software.) iCMTGIS II only works on an iPad device. Its iPhone equivalent is the iGPSGIS II app.

iCMTGIS III and iCMTGIS PRO can run on iPad and iPhone devices. These two apps will let you load a GeoTiff image or a .pim image as background map. They also provide a built-in Attribute List from which you can choose as additional Attributes for the Features. One of the screen shots displayed here shows the current list of built-in Attributes that you may elect to include in the data records for the Features recorded using GPS. Other additional functions are also provided in these apps, which help you stake points/lines/areas, create Features by entering distances and bearings, as well as classify, sort or perform a search on the Features in a Topic layer, import and export Point Features via a text file, etc.

GPS surveying using iPhone

GPS surveying using iPhone

iCMTGIS PRO has all the functionality of iCMTGIS III plus the Contour/Volume and Create Buffer functions. What sets it apart from the other two apps is that it provides the ability to receive the NMEA message stream directly from a few specific external GPS receivers. When the “Enable the External GPS” option is selected, iCMTGIS PRO will get the GPS information directly from the external GPS receiver rather than the iOS CoreLocation. This enables it to display a GPS status bar in real time.

At this time, EOS Arrow GPS receivers and Geneq iSXBlue II + GNSS can work in the “Enable the External GPS” mode. To use the EOS Arrow 200 and iCMTGIS PRO for RTK work, you must use the free EOS Tools Pro app to connect to the RTK network.

Which of your apps, if any, allow me to measure area by walking the perimeter with my iPhone?

iGPSGIS II provides the function for you to log GPS data continuously on your iPhone while walking the perimeter of an area that you wish to measure. You can then view the perimeter and area of the Area Feature created in this way.

Keep in mind that the accuracy of the measurement depends on the accuracy of the GPS used. Many of our customers use a compatible external Bluetooth GPS receiver, such as the Dual XGPS-150A or the Bad Elf GPS, to get 2-5 m horizontal position accuracy.

New Release: Forester GPS GSI II for iPad

IN Tree

IN Tree

We are pleased to announce the release of Forester GPS GIS II for use on the iPad. This app provides GPS data collection and mapping functionality in addition to the various utilities provided in the original Forester GPS GIS app.

“Forester GPS GIS II” provides tools for estimating basal area per acre for a timber stand as well as GPS data collection and mapping functions for use on the iPad. It will let you use a GPS receiver to map a timber stand or any other land parcel then create grid points over the area. You can also create features by importing feature data in Shapefiles or DXF format, by manual digitization or by entering deed calls. The acreage and perimeter of an area feature will be promptly computed. You can easily divide or combine the land plots. You will be able to record attribute information for each geographic feature. You also will be able to export the feature data as Shapefiles in LLA, UTM or State Plane coordinates.

If your device has GPS capability, the Point Stakeout function could help you locate the cruise points, and the Line Stakeout function could help you stay on a transect line. The accuracy of the location data depends on the GPS receiver used.

Off-line GPS data collection

“I would like the ability to collect points, lines, and polygons in the field, offline, with a way to easily download them as shapefiles for use in ArcMap when I return to the office. Will I need to purchase anything else in order to do what I have indicated?”

iCMTGIS II and iGPSGIS II will let you collect points, lines, and polygons in the field, offline, and you can download them as Shapefiles for use in ArcMap when you return to the office.

As far as off-line GPS/GIS data collection and Shapefile import/export goes, iCMTGIS II or iGPSGIS II is all you need.

The questions is whether you need to have a background map displayed as reference while collecting GPS/GIS data.

When you have connection to wi-fi, you can have the standard or satellite Apple Map displayed as background map.

If you have Shapefiles for the region in which you will be collecting data, you can import those into iCMTGIS II or iGPSGIS II as off-line background reference.
If you need to have an off-line geotiff background map displayed during data collection, then you will need to get the PC-GIS 09 mapping software, which will convert geotiff images to the .pim format for use with iCMTGIS II or iGPSGIS II.

Does the app “Area – Distance” allow a person to walk a perimeter to determine the area of a field?

The Area – Distance app is mainly for digitizing a line or an area on the displayed Apple Map then determining the distance or area, respectively. If you are using an iPhone or an iPad with built-in or external GPS, then you could use the Pick GPS function to drop nodes manually as you walk a perimeter to create the Area Feature.

However, the proper way to map a field using GPS is to use the Data Collection function provided by iGPS GIS II for iPhone, iCMTGIS II for iPad or Utility Data Collection for iPad. Using the Data Collection function, you can specify how often to drop a node (default is once a second) and you can also record one or more descriptions for the Area Feature. The app will do the area delineation for you as you walk the perimeter. If the area is a polygon with straight sides, the app also provides an option to record just the corner points to create the Area Feature.

Will iGPSGIS run on iPOD touch?

Yes, iGPSGIS will run on iPOD touch (iOS 4.3). You will be able to digitize Points, Lines and Area Features and enter Attribute data for them. However, in order to obtain GPS positions, you will need to connect your iPOD touch to an external GPS receiver.