Automatic Magnetic Declination in ike

The digital compass in ike uses magnetoresistive sensors to measure the heading to magnetic north, but to calculate the correct position of a remote target, the heading to true north is required. To calculate true north, the magnetic declination must be known. To make matters worse, magnetic declination varies not only with your location on the earth, but also drifts over time. However, all of these difficulties are easily overcome using ike's automatic magnetic declination feature.

The National Geophysical Data Center (NGDC) provides a mathematical model of the magnetic field worldwide, that can be used to calculate the magnetic declination for a specific location at a specific time http://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml.

ike uses this mathematical model, along with the current time and your GPS position to update the magnetic declination each time a new GPS reading is received, so you're always up to date.

I recall once many years ago I had to demonstrate an ike unit in Taiwan before we had automatic magnetic declination implemented. I had forgotten to check the magnetic declination before I left home, and didn't have Internet access. I had to find two find two landmarks about 100m apart, measure their GPS positions using ike, work out the true bearing between the landmarks using ArcPad, take bearings between the landmarks using the compass in ike, and finally calculate the difference between the true bearing as indicated in ArcPad, and my measured value to compute the magnetic declination... It did the trick, but boy what a hassle!

These days I just leave the "Automatic Magnetic Declination" option enabled...

ikeOS 3.1 beta !

We've been working hard here in the Surveylab engineering department to get ikeOS 3.1 up and running, and we've finally got a beta release available, and customers having a try of the new software.

The really exciting new aspect to ikeOS 3.1 is the use of EXIF information to embed all of the geospatial information associated with an iked photograph directly into the JPEG image file.

The new "ikeCapture" application can be invoked from any application that can generate an XML configuration file, and send Windows messages. The calling application creates the config file, sends the "GO" Windows Message to ikeCapture, and then waits for the requested image to be created. Then the application can extract any of the measured information (ike's location, target location, bearing, PDOP etc) from the EXIF metadata. Alternatively the image can simply be saved, and the metadata extracted later. This concept makes integrating ike into new GIS applications very straight forward.

We've set up an ArcPad extension to help with this, so it's very easy to work with ikeCapture from ArcPad with minimal modifications to existing shapefiles. The ArcPad toolbar has been extensively reworked, and now supports creation of Points, Polygons, and Polylines using any combination of remote and local positions (e.g. stand in one corner of a field, use local position for first vertex, and remote position for the remaining 3 vertices). Existing features can also be edited after the initial capture (great for capturing three sides of a building initially, and then walking around to the back of the building later to capture the final vertex).

For those who don't use ArcPad, we've also created the "ikeIt" application, which launches ikeCapture to create geotagged JPEGs, and appends the geospatial information to a CSV file (same output format at the Standard DCA included in ikeOS 2.6).

If you would like to be involved in the beta program, or need more information, please contact support@ikegps.com.

Surveylab at ESRI Federal User Conference

Surveylab regulary exhibits at the ESRI Federal User Conference in Washington DC. Its great to catch up with our existing customers, and meet a new ones. Pictued, is Ed Sanford (VP US Sales) and Jeff Stewart (Federal Account Manager)