Can I attach a photo to a Feature?

The back-end mapping program, PC-GIS 09, will let you link one or more photos that you have taken at the work site to the relevant Feature. It will also let you link a video and a voice recording or an ODBC object to the same Feature.

Another CMT mapping program, PC-MAPPER 09, provides the option to automatically match the photo files to the Features based on time.

Can I use my own aerial photo as background image?

Your own aerial photo in the form of a JPG or TIF image file has most likely not been geo-referenced. This means that the GIS mapping software will not be able to place the aerial photo at the location that it represents.

PC-GIS 09 will let you register the location of the aerial photo based on a number of reference points. Essentially, you will match the reference points with known coordinates to the corresponding points on your aerial photo, and PC-GIS 09 will register this information and permit the photo to be displayed at the proper location on the GIS map screen.

Please click on the link for the Geo-referencing DEMO on the right side to see how this is accomplished.

After the aerial photo has been geo-referenced, you may load it into PC-GIS 09 then convert it into a .PIM file for use with iCMTGIS or iGPSGIS.

Can I get a DEMO version of PC-GIS?

Yes, please click on the PC-GIS DEMO DOWNLOAD page to see the download instructions.

Acreage determination

You can use iCMTGIS or iGPSGIS to determine the acreage of a region as follows:

1. Create the Area Feature for the region

You may do so by digitizing the area as shown in our previous article. You will want to load a Google Map or some other raster image to use as a reference.

If feasible, you could also map the area by walking around it and using the GPS data collection function to record the Area Feature.

2. In Map View, tap the Area Feature to select it.

3. Tap the Feature Properties tool icon (showing a pair of spectacles) then tap the Length/Area button to display the perimeter and area in various units.

Alternatively, in iGPSGIS, select Main Menu, select Utilities then tap the View Area/Length tool to display the length and area information in the lower portion of the screen.

Alternatively, in iCMTGIS, select the Measure tool icon then tap the View Area/Length tool to display the length and area information.

See also: Tony Edwards’ Program Notes

How to digitize an area?

As we mentioned before, if you wish to have the area computed for a region of land or water on a raster image, you must first draw the boundary line around that region and save it as an Area Feature. An Area Feature is a vector shape and can be saved in the shapefile format.

To digitize an Area Feature in iCMTGIS or iGPSGIS, first select an existing Area Topic or create a new Area Topic.

To create a new Area Topic, tap the Main Menu, select Topic then select New Topic. Enter a Topic  Name, such as “Fields”. Make sure the Type field shows: Area. Tap the green check mark to confirm the screen and return to the Map View.

To activate an existing Area Topic in order to add a new Area Feature to this group, tap the Topic View icon on the upper-right corner of the main screen then select the desired Area Topic. Tap the Topic View icon again to hide the list of Topics.

When an Area Topic is active, and you tap the pull-down arrow for the Tools icon next to the Main Menu icon, you will see that the Add Area manually tool is active (not grayed out). Tap this selection, and the Add Area manually tool icon will be displayed.

Now, tap the vertices of the desired polygon, or trace the curvilinear outline of an irregular area.

While you are digitizing, if you need to zoom in or out, first tap on the little hand with a pointed index finger. This will halt the digitization mode and reactivate the regular touch-screen mode. Tap on this toggle again when you are ready to continue with the digitization.

If there are existing Features on the map and you want a node to snap to one of the existing Features, then tap the SnapTo Node tool showing an arrow pointing to a node. When the SnapTo Node toggle is on, the node you add will be dropped on top of the nearest Point or node.

When you have digitized the last node for the Area Feature, tap the Add Area manually tool again. The software will automatically close the gap between the first and the last digitized nodes.

GIS and You

Map showing attribute table for the Samples topic layer

Advances in mobile GPS devices have now made it possible to easily record GPS locations along with the associated feature information to be fed to a Geographic Information System (GIS). So you’ve gained a general understanding of GPS and know how to use your mobile device to acquire and record GPS data. You’ve also learned how to add descriptive or numeric attributes to the GPS Features. And you’re probably exporting the field data to a mapping software to analyze the data and to produce reports and an informative map for your project. But what actually is your project about? And where else can you apply your GIS skills?

A very popular area of GPS/GIS application is forest land management. GIS-grade GPS data collectors have made it easy to navigate around a timber stand and record the Area Feature and record the timber stumpage along with any remarks and descriptions. A modern mobile device with a color display will let you see exactly where you are located on the background topographic map or aerial photo. For large management projects, you can bring in data collected using a number of data collectors and combine them in the same job file in the desk-top mapping software.

Farmers and fruit growers are using software to layout the plots and plan their crops before the actual planting.  They also keep the fertilization and harvest information in a database for  optimization analysis. Wildlife specialist use GPS/GIS to track animals and invasive plants in the wilderness. Governments employ GIS in epidemiology and in studying insect infestations in forests. They also conduct air-borne surveys to collect GPS/GIS data for military reconnaissance and natural resource management.

More and more cities, airports, schools as well as oil and gas companies are utilizing GPS/GIS to help inventory and manage their assets. They now have at their tips all the information that previously required tedious manual entries and were prone to recording and transcription errors.

GIS is not just for the military and civilian professionals. When you engage in geo-caching or orienteering, you are making use of GIS.  When you look up a travel destination on Google Maps, you are making use of GIS. In fact GIS could be used to advantage in almost every aspect of life that you can think of. The blog post at this link shows an interesting video about how, armed with GIS data, one could even choose where to live for the sake of one’s health (I must add, if one could afford to do so).

GIS has elevated our awareness of where we are with respect to  our immediate environment to the realization that our location represents but one coordinate point on the map of the world, and yet the sample that our particular data represents contributes to and impacts the entire population data set.

How are you using GIS on your job or in your leisure time? Please share your interesting application stories with your fellow earthlings.

Which coordinate system to use?

By default, most GPS receivers and application software use the Lat-Lon-Altitude (LLA) geographic coordinate system based on the WGS84 datum. In this system, the horizontal positions are expressed in terms of angular measurements (degrees, minutes and seconds). As it is much easier to compute distances and areas using linear units in a Cartesian coordinate system, many GIS professionals and surveyors prefer to work with a plane projection, such as the State Plane system in the USA and the global UTM system.

iGPSGIS and iCMTGIS will let you  select the coordinate system and datum to use for displaying the position data. To do so, first tap the Main Menu icon. Select Setup then select Coordinate System. Pick the coordinate system of your choice.

If you will be using a Google Map as a background map for data collection or navigation, then use the default LLA system because this is what Google Maps are based on.

To use the State Plane system, select “State Plane” and accept the displayed  “NAD83_CORS96/CSRS98″. Then select your state and the Region code, and enter the Zone number. Accept “US Survey Feet” as the distance unit.

The Lat-Lon-Altitude (LLA) system and the UTM system default to Meters. If you wish to work with distances in feet, then for the Unit field select “US Survey Feet” or “International Feet”. The difference between these two units is insignificant when working with non-survey grade GPS receivers.

Tap the green check mark at the top of the screen to save your settings.

Expediting data collection

Using a Feature List for data collection speeds up the data input tremendously. You can take this one step further by specifying a default description for each Feature Attribute of interest.

For example, you’d probably expect most of the fire hydrants to pass your inspection. Therefore,  in the ht.fbr Feature List,  you would want to specify “Pass” as the default value for the “Condition” Attribute of the Hydrants Feature Topic. 

To do so, first open the ht.fbr Feature List . Highlight the “Hydrants” Feature Topic then tap the Attribute tab at the bottom. Select the “Condition” Attribute then tap the Value tab at the bottom. Tap the Default box for the Value “Pass”. Tap the Save button to save your selection.

If you wish to also set a default value for the “Type” field, tap the Attribute tab then select “Type”. Then tap the Value tab and mark the Default box for the desired Value.

The screen to the right shows the selection of “Medium” as the default Value for the “Size” Attribute of the “Trees” Feature Topic.

The default Values that you specify will automatically fill the data input field for data collection. While enjoying this convenience, please remember to select the appropriate description from the predefined List of Values when you encounter a Feature that does not conform to the norm.

Furthermore, if for instance you come to a street tree that’s not any of the predefined species, you could manually enter its species name into the Value data input field. However, if your GIS system cannot accept any species data outside of the predefined list, then you could lock the “Species” Attribute. The Attribute Lock box is located to the right of each Attribute. Activating the Attribute check forces the user to enter only those Values listed in the Feature List for that Attribute. This option prevents the user from entering unwanted or misspelled values.

Similarly, activating the Lock box for a Feature Topic will force the user to enter only Feature Topic names contained in the Feature List. This option prevents the user from entering unwanted or misspelled Feature Topics. If this box is not checked, the user is allowed to enter any Feature Topic name through the keyboard of the data collector.

Once you have completed the setup for the ht.fbr Feature List, you may associate this Feature List with any data collection job that calls for the same Features, Attributes and Values setup.

Defining GPS data collection parameters

For the sample data collection job that we are discussing, our goal is to inventory all the fire hydrants and all the street trees in a section of a city. 

Normally, you would use the CMT PC-GIS software to easily set up one or more Feature Lists then port them over for use on your iCMTGIS or iGPSGIS. However, if you need to create a new Feature List or modify an existing one in the field, you may do so by using your iCMTGIS or iGPSGIS. The procedure is as follows.

Tap on the “GPS” icon then select Feature List.

Tap the “Open” button and select the built-in Feature List, named park.fbr. Tap the “Save As” button and save it as a new Feature List under the File Name ht.fbr.

Keep the “Tree” Feature Topic and delete all the others.

Double-tap on ”Tree” then add an “s” to it.

Tap the “Add” button and add a new Feature Topic, named “Hydrants”.

Now we have our two Feature Topics of interest: “Trees” and “Hydrants”.

Tap the Tree Feature Topic and make sure the Type field shows “Point”, and the Mode field shows “Static Time”. Change the Time Session to 30. This is the number of seconds you are supposed to stay at each street tree to record its GPS location.

Do the same for the “Hydrants” Feature Topic because these are also Point Features.

The data collection parameters you specify for each Feature Topic will be displayed as the default settings when you select that Feature Topic to collect data for it. You may override the default settings for the Mode field and its associated time parameter.

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If you were asked to record the street as a Line Feature, then you would add a new Feature Topic and select “Line” as the Type and “Dynamic Time” as the Mode. The Time Interval field defaults to 1 (GPS fix per second) but you could change it to a higher number if you just want to trace the path roughly.

Similarly, if you were recording the perimeter of a park as an Area Feature, then you would add a new Feature and select “Area” as the Type and “Dynamic Time” as the Mode. You could use the default Time Interval of 1 second, or change it to some other value.

If you were recording a polygon shape and do not care about the nodes between the vertices, then you would select “Area” as the Type and “Static Time” as the Mode. In this case, you would occupy each vertex for the duration of the Time Session to record its location. And nothing would be recorded while you walk or drive from one vertex to the next.

Designing a GIS data collection job

Suppose you are assigned the task of using a CMT GPS field data collection program to inventory all the fire hydrants and all the street trees in the southeastern section of the city. The data will be incorporated into the city’s GIS database.

Some factors to consider for a GIS data collection task are:
1) Feature Topics of interest
2) How long to occupy each point, or how often to record a node for a path
3) Feature descriptions of interest

For this job, the geographic features of interest are Fire Hydrants and Street Trees. These are considered Point Features because only one  (X,Y,Z) position will be recorded for each item. As the Fire Hydrants and the Street Trees do not share the same set of attributes, you want to group them into two separate Feature Topics.

How long to occupy each point depends on the quality of the GPS receiver and the accuracy requirement of the data collection job.

The data collection software will record the location coordinates when it is able to compute a solution for the occupied point.

Your GIS analysts will tell you what descriptions they would like you to record for each Feature Topic. Let’s say, the attributes of interest for the fire hydrants, are:  Type and Condition, and the attributes of interest for the street trees are:  Street Name, Species and Size.

You could simply grab your data collector and head out to record the GPS coordinates of each fire hydrant and street tree, and busily enter the description for each entity.

Or, you could set up a Feature List ahead of time to facilitate the data collection process. Basically, a Feature List contains the setup for one or more Feature Topics, each with its associated data collection parameters and Attribute/Value database. When you use a Feature List with a data collection job, you can simply confirm the displayed data collection parameters; and you will be able to select the appropriate Attributes and Values rather than having to manually enter the descriptions.

Essentially, the Feature List embodies the design of your data collection job. A well thought out data collection design will produce well organized and consistent data that will be useful to your GIS analyst.

Preparing for a GIS mapping job

You will be able to perform your data collection job more efficiently if you plan ahead and get the answers to the following questions first.

1) What are the accuracy requirements on the GPS data to be recorded?

Barring human errors, your GPS data will be as good as your GPS data collection system. Please keep in mind that, at this time, mapping grade GPS devices are like measuring sticks with 1 – 5 m graduations.

2) What type of Features will you be mapping?

Some people are only intersted in mapping Points. Others may also need to map routes or areas. When you map a path or an enclosed area, please keep in mind that the attribute information will be recorded for the entire Line Feature or Area Feature, rather than for each node on these lines or areas.

3) How long do you plan on occupying each Point? How often would you like to log GPS positions while moving along a path?

You know, instead of entering this parameter for each Feature that you record, you can predefine it in a Feature List using iGPSGIS or iCMTGIS. Then whenever you select a Feature Topic from the Feature List to log data for it, the relevant data collection parameters will be automatically applied.

4) What attribute information would you like to record for each Feature Topic?

If you collect data for multiple Features with different characteristics, you want to organize them and group similar Features into Feature Topics. You can define a set of Attributes for each Feature Topic and also pre-define the Values for each Attribute. When using such a Feature List for data collection, you can easily select the applicable descriptions for each recorded Feature instead of entering the descriptions by hand.

5) Will you need to use existing data or a background map as reference for this data collection job?

iGPSGIS and iCMTGIS can display a Google Map as the background.

PC-GIS PRO will let you import data in various popular formats then save it in a .pmp file for use on the iGPSGIS for iPhone, iCMTGIS for iPAD, or Field CE GIS for Windows Mobile PDA. It will also enable you to prepare raster images for use on the mobile device.

If you have a Windows-based tablet PC or notebook PC running PC-MAPPER, then you can load the background image in various formats (e.g. TIFF, GeoJpeg, MRSID, ECW).

PC-GIS PRO and PC-MAPPER will let you geo-reference your own aerial photos for use as background maps.

The CMT PC software will also covert the neat CMT Basemaps into a format that can be used in your iOS or Windows Mobile device. The PC application can even let you select roads and landmarks from the CMT Basemap to convert them into Features.

6) Do you need to visit known locations to record new observations?

You could import these locations as Shapefiles. Or, you could digitize these locations in iGPSGIS or iCMTGIS.  Then edit the coordinates to match those for the exact location.

PC-GIS PRO and PC-MAPPER will also let you import coordinates in other formats (e.g. ASCII, DXF, Excel, KML, GPX).

7) Does your data collector have sufficient power in it to complete the job?

Make sure the battery in your data recording device is fully charged. Take an extra set of battery along if the device will use replaceable battery.

8) Are the GPS satellites up there favorably configured?

Once or twice a day, the relative positions of the GPS satellites may be such that the location solution cannot be precisely determined. This type of error is called DOP (Dilution of Precision). If you have the CMT PC-GPS or PC-MAPPER software, you can use the Mission Planning function to find out ahead when those peaks occur on the day you plan to do your field work. Otherwise, when you see that the horizontal/vertical accuracy displayed in iCMTGIS or iGPSGIS is not good, you can try waiting half an hour then resuming your job.

We’re a small non-profit organization. What will it take for us to do some resource mapping?

Please read our 6/24/11 post, titled “What makes up a GIS data collection system?”

If the people in your organization own an iPhone or an iPAD, you could use iCMTGIS or iGPSGIS to collect field data, and the CMT PC-GIS 09 desk-top software to print the map and manage the data.

If you own a  Windows Mobile PDA, please log on to www.cmtinc.com, scroll down a little and click on “Field CE GIS” to see information about the data collection software desgined for use on Windows Mobile PDA.

What makes up a GIS data collection system?

Modern GIS technology automates the process of data collection and provides media to store tremendous amounts of data that if printed out would inundate many a brick-and-mortar library.

What makes up a GIS data collection system? The major components of a general GIS data collection system are:

Data recorder
GPS receiver
Data collection software
A person or a remote control mechanism
GIS/Mapping office software

Specialized data collection systems may incorporate additional hardware (such as depth sounders and laser guns) or software to record specific pieces of information.

The present market is filled with a wide variety of devices that could be used for GPS/GIS data collection. There are the tiny mobile phones and PDAs with or without built-in GPS, there are notebook PCs for those who prefer to work with a large screen, and in between are the tablet PCs with a medium-size screen.  While it’s nice to be given choices, the newcomer is often daunted by the many possibilities. Some of the factors to take into consideration are: GPS capability and other functionality, price, ruggedness, display size and readability under sunlight. If you already own an iPAD or an iPhone, you might consider using the iCMTGIS for iPAD or the iGPSGIS for iPhone.

Equally important is the choice of the data collection software to run on the data recorder and the software for mapping and organizing the data. Again, there are quite a few selections available. Of course, the software must be compatible with your GIS data recorder hardware. It must be able to perform the required tasks and be easy to learn and use. It will also need to fit into your budget.

At the minimum, the GIS data collection software should let you record the GPS coordinates and a description for the Features of interest. It should let you output the data to your GIS/Mapping software. Your GIS/Mapping software should let you view the collected data on a map and also store it into a file or an industry-standard database.

When looking for a powerful and affordable GIS/Mapping software to complete your GPS/GIS data collection system, please compare its functionality to that provided by the CMT PC-GIS software:
http://www.cmtinc.com/software/PCGISPro.htm

What is a Feature List?

With GPS/GIS data collection, the primary interest is to log the GPS position and record the information associated with that location, be it a Point position, a Line Feature like a road or a river, or an enclosed Area.

The CMT GPS/GIS data collection software will let you specify the GPS data collection parameters as well as enter the descriptive information for the recorded geographic feature.

This field data entry process can be streamlined by the use of a Feature List.  The Feature List is a database that you can pre-define to contain the listing of the Feature Topics that you wish to map, the data collection parameters for each Feature Topic, as well as the associated Attributes for each Feature Topic.  In addition, you can define the list of your standard descriptions for each Attribute.  

When you use a Feature List with a job on the field data collection program, all you need to do is to select a Feature Topic for which to record data, confirm the data collection parameters, select the desired Attributes/Values then log the position. This minimizes the amount of information you need to manually enter, and ensures accuracy and consistency of the recorded GIS data.

The Feature List can be created on the CMT GPS/GIS  field application, or on a CMT PC mapping software program. 

 

 

GPS for Navigation

Another popular use of GPS is in navigation. For this type of applications (e.g. geo-cashing), a specific destination is given, and the GPS navigation program will guide you toward it based on the position information provided by the GPS receiver. 

An advanced GPS program, such as CMT Field CE GIS, PC-GIS or PC-MAPPER, will include functions to help you navigate to a destination point or along a route that you specify, and provide graphic as well as verbal turn-by-turn directions.