Map, Compass & GPS

Map, Compass & GPS
Wild flowers along Fall Creek on the way to the Green Lakes - Oregon

Tuesday, November 27, 2012

GPS Accuracy

A friend from my SAR team forwarded Michael Coyle post on GPS Accuracy.  Don't get too wrapped up with the complexity but take away the basis of your receiver's accuracy calculations. 

Your GPS is lying to you

At the very least, you’re probably misinterpreting what it’s saying.

People’s attitudes toward GPS devices are very interesting. Since 2000, when selective availability was turned off, GPS has become ubiquitous to the point where most people have one and interact with it on a daily basis, whether they know it or not. To make things even more confusing, the general case of global positioning, whether satellite based or not, is completely pervasive. You may not know this, but this web site knows where you are (to some level of detail) right now.

To read the rest of Michael's post go here.

Monday, November 26, 2012


REI is offering the SPOT II for around $75.00.  Excellent price.

Tuesday, November 20, 2012

GPS - Returning To A Destination

This post covers several GPS considerations before striking out for a destination.

The hike into the backcountry has come to an end.  Now it’s time to return to the trailhead.  By selecting “Find” or “Where Is” the GPS receiver provides direction to the trailhead.

Figure 1.  Using a magnetic compass.

Before returning, the hiker should review several GPS navigation considerations:

·         The Electronic compass:  It must be calibrated after each battery change.  If the hiker doesn’t remember doing this, calibrate the receiver.  Bearing information will be more accurate by several degrees.

Figure 2.  GPS Compass display.  The bearing to the destination is 298°.  The hikers heading is about 115°.

·         Distance information:  This data (e.g., 10.2 miles) is line of sight or more commonly, “as a crow flies.” The GPS receiver doesn’t take into account topography and detours that may be needed.  Thus, a distance of 10.2 miles may really be 11.2miles or more at the end of the hike.

·         Bearing: Make sure that bearing information is presented in degrees and not “cardinal letters” such as NNE (North North East).  The hiker’s compass provides direction information in degrees.  When aligned this keeps navigation simple; both compass and GPS complement each other.  Make this change by adjusting the compass setup.  

 As shown (figure 2 above), the GPS provides direction (298°) and distance (10.2 miles) to the waypoint.  The direction is the “Bearing” to the waypoint.  The red arrow and digital read out provide the return direction to the waypoint, in this case is 298°. (The red arrow points the hiker to the waypoint.)  As the hiker moves down the trail, expect the receiver to provide continuous updates to the selected destination.  Movement on the will may cause the red arrow to move and the digital information to change too.

 Note that the return direction (Bearing) to the original waypoint may very likely be different than the heading as the hiker moves down the trail.  Heading is the hiker’s direction of travel, his path through the backcountry.  In the example (figure 2 above) the heading is 115°; the direction of movement.  Later, as the hiker moves directly to the waypoint, both the bearing and heading may be the same.


·         GPS Map Page: Select the map page.  Use this page to corroborate the electronic compass information. 

Figure 3. The blue squiggly line is the recorded track; it is where I have been.  The black triangle indicates my position on the map page and the direction travel. 

  •  In this view, the wide blue line is the GPS track; the hiker’s historical path through the woods.  The exaggerated black triangle points in the direction of travel. (The other red and brown lines are logging roads.)  To obtain this type of presentation the GPS has been left on capturing satellite data during the entire hike.  Using the black triangle, the hiker can follow his movement down the trail to the waypoint destination such as “CAMP” at the bottom right of the screen.

·         Bushwhack:  Occasionally the hiker may elect to bushwhack from a current position to a new destination.  The hiker should consult the map to assess the overall big picture to determine if the route is safe, find and identify natural obstacles and evaluate terrain.


·         Map and Compass:  Don’t leave these important tools stuffed away in the pack.  Practice with them during the hike.  For example, use the map and compass to orient the map to get the general lay of the land.  Use the compass to further evaluate the bearing to a destination.  For example, the GPS’ determines that the bearing to the trailhead is 298°.  Use the compass to sight a bearing of 298° and follow the compass rather than the GPS’ electronic compass.

Navigation is not hard but it takes practice and repetition.  Don’t assume you will have the same visual landmarks on the return trip.  A change in weather (fog and snow) can increase the complexity of your navigation.  Practice and experience significantly helps develop confidence in the hiker’s skill level and equipment.


Friday, November 16, 2012

Orienting a Map

Orienting a map is a starting point to identify where I am, where I want to go and where I have been. I orient my topographic map (topo) before I leave the trail head and at regular intervals during a hike.

To read the rest of this post go here.

REI sale on GPS Receivers

Check out REI's sale on Garmin GPS receivers here.

Wednesday, November 14, 2012

Battery Power For The GPS

Check out my latest article about batteries and power management for your GPS at SeattleBackpackersmagazine.  View it here.

Monday, November 12, 2012

SPOT Support For a Rescue

From the Billings Gazette:

November 08, 2012 12:10 am
"It seems wrong to say that Columbus elk hunter John Chepulis was lucky. He’s lying in a Bozeman hospital intensive care room hooked up to a ventilator to help him breathe, heavily sedated and fighting pneumonia. But his situation could have been much worse.

"This whole thing, to me, has been divine intervention from the beginning," said Bonnie Chepulis, John's wife.

Chepulis, 65, was hunting with friends John Simmons and Scott Wittman near the base of Shedhorn Mountain southeast of Ennis on Oct. 30 when everything went haywire at about 10 a.m."

To read the rest of Brett French's article go here.

Parachute Cord

The following post is from Peter Kummerfeldt's blog:

550 cord, paraline, paracord, parachute line, call it what you will, 150 feet of mil-spec parachute line should be a part of your gear.

As I think back over nearly 46 years of teaching survival skills and about the same amount of time beating about the bush, I don't think I have ever been without some parachute cord. I have used to to build shelters, catch fish, weave nets, make stronger rope, for emergency dental floss, as sewing thread, to retrieve water when I was cliff-bound and yes, parachute line has lowered me to the ground when I jumped out of an airplane while I was in the Air Force. Simply put it can truly be a life saver!

To read the rest of Peter's post go here.

Deschutes County SAR - Join Us

Deschutes County Search and Rescue is looking for new team members.

If you are interested down load the application here.