Benchmarks On a Map

                                              

When looking at a US Geologic Survey (USGS) map the hiker will find benchmark symbols sprinkled across the topo.  Benchmark and the many other symbols provide the details of a map.  Symbols represent features such as mines, bridges, dams and many more items.  To see a complete look at symbols visit the USGS site for more information.

Figure 1 Symbol examples from the USGS Topo Map Symbols web page.

Figure 2  Benchmarks on a topographic map.

A benchmark is control point on the map.  Control points are positions of accurate measurement in terms of elevation and position (latitude and longitude.)  Benchmarks are also known informally as “survey markers.”  Originally, these markers were used in land surveying and by civil engineers for construction purposes.  Benchmarks help to accurately determine location.

From www.mytopo.com’s frequently asked questions: 

“A benchmark, abbreviated "BM," is a location whose elevation and horizontal position has been surveyed as accurately as possible. Benchmarks are designed for use as reference points, and are usually marked by small brass plates.”

Occasionally the hiker will find a benchmark plate in the backcountry.  The image below is an example of the brass plate.  These plates should not be tampered with and are not souvenirs to be taken home.

Figure 3  Brass benchmark found in the backcountry.

Note the elevation data found in the center of the plate.  Importantly, the elevation information is measured in feet above sea level and not in relation to the adjacent topography.  Wikipedia.com reports that over 740,000 benchmarks are dispersed around the United States.

Though elevation data is provided on the map, coordinate information (e.g., latitude and longitude, UTM) is not.  It’s is up to the hiker to interpolate and determine the information through the use of a map tool.

Remember that the coordinate data provided on a topographic map is in degrees, minutes and seconds (GPS menu settings format: dd mm ss.s) while a new GPS is set at the factory to degrees minutes.minutes (GPS menu settings format: dd mm.m.)

Finding a benchmark can confirm your position on the map. 

To improve you GPS skill level try “Benchmarking,” an activity similar to geocaching.  The objective is to find the brass plates in the field.  For more information visit Geocach.

Monitoring Backcountry Weather - Part 2

I use my GPS receiver to provide barometric pressure information while hiking in the backcountry.  Barometric pressure data gives the hiker an idea of how the weather is developing and changing.

My weather training began while serving as a deck officer aboard navy destroyers in the 1970’s.  I was specifically directed to monitor the atmospheric pressure while at sea.  In the days before satellite imagery and modern meteorological equipment, barometric pressure was recorded and monitored hourly with weather reports sent to the fleet forecasting center approximately every four hours.   Aboard the ship, the Captain’s standing orders required that I notify him if the barometric pressure dropped more than .04 inches of mercury in four hours; this was a big deal.

As an outdoorsman, I continue to keep a sharp eye on the weather while afield.  At home I frequently check my internet sources such as 

WeatherUnderGround  and watch the weather reports each morning.  In the camp I have a radio with the NOAA broadcasts. 

I also enjoy reading information about the weather.  An excellent reference is Northwest Mountain Weather by Jeff Renner (published by the Mountaineers).  Though out of print, copies are available online through www.alibris.com at $0.99 each (not including shipping.)  Renner is professional meteorologist and broadcaster.  He is an outdoorsman and flight instructor.

Renner’s book provides a superb overview on how “the weather works” in the Pacific Northwest.  Uniquely focused to this region, this book provides an overview on the climate and weather, local weather patterns, snow and avalanche conditions and many charts and data sources. 

My personal favorite is Chapter Seven’s “Field Forecasting Guidelines.” This chapter identifies how to watch for and monitor weather system changes. In the subsection “Clues from Pressure Changes” Renner states:

“Remember that a pocket altimeter can give excellent indications of an approaching weather system.  An altimeter that registers an increase in altitude, even though none has taken place, is actually reporting a drop in air pressure.  Changes in pressure create changes in wind and are often related to approaching fronts that may bring precipitation.”

The comments regarding the pocket altimeter apply equally to a GPS receiver equipped with an altimeter.

Following this discussion is a short table regarding pressure drop.  The following is an excerpt and is what I keep an eye on:

         

Many of the newer Garmin receivers have barometric altimeters.  The Altimeter display can be adjusted provide a Pressure Plot.  An example is shown below.

The green plot illustrates the trend of pressure change over time.  This plot was developed over a 40 hour period for illustrative purposes.  The receiver remained powered up the entire time.  (Turning the receiver off or changing batteries erases the historical data.)

Pressure measurements need not be accurate, it is the trend of information that the hiker is interested in.  A near vertical drop in a short period of time is what we are looking for but hope to avoid: time to look for shelter.

Coupled with observations of the cloud type, temperature and wind, the barometric pressure plot will give the hiker information about how the weather is changing.

Monitoring Backcountry Weather - Part 1

Monitoring  and tracking the weather is a pastime of mine.    Recently my son reminded me of a little known theorem that helps the hiker’s situational awareness.  This theorem is called Buys-Ballot’s Law.

In 1857 Dutch professor Christopher Buys Ballot postulated that there was a relationship between wind direction and air pressure. Buys-Ballot’s law provides a rough approximation of the location and direction of the low pressure system as it tracks through a region.

Simply put in the northern hemisphere, if one faces the wind, the center of a low pressure system will be to the right and slightly behind the observer.  High pressure will be to the left and slightly ahead of the observer.   Further, weather systems in the northern hemisphere track from west to east.  

Importantly for the hiker, a low pressure system is associated with rain, snow and bad weather in general.  A high pressure system is associated with improving weather conditions.

So, if the hiker determines that high pressure is to the west of the present location, and because the system will move from west to east, the weather may be improving.

The YouTube video by meteorologist Vince Condella presents this nicely; video. 

Buys-Ballots Law coupled with a GPS are both useful tools to improve the hiker’s ability to monitor and anticipate the weather in the backcountry.

Satellite Navigation System

After 17 years of development the Galileo Satellite system is on track for full operation.  Galileo is a European program similar to GPS.

Garmin has been working with the Galileo program for over a decade.  Look forward to a new receiver coming too you soon.

Galileo 

Compass Accuracy

Navigating with a magnetic compass is a skill that takes study and practice.

When plotting the hiker’s position on a map the objective is to have three lines of bearing intersect just like in the image below; this is a position fix.  That is “pin point” accuracy. This is hard to do with a magnetic compass and may not be achievable.

Blake Miller/Outdoor Quest Image

Many factors impact accuracy.  Some the hiker will have no control over.  

These include:

1. Visual acuity (e.g., how well the hiker can see.)
2. Polarity of the compass’ magnetic needle – does it point in the right direction? Polarity may change over time such that the magnetic needle may no longer work accurately.
3. Smooth movement of the magnetic needle.
4. Alignment of the compass dial to the compass housing.
5. Local attraction – Similar to declination, local attraction is magnetic interference unique to a specific location.  It may be caused by buried metal objects or an unusually high concentration of iron or nickel in the ground.
6. Lack of distant objects to sight on.
7. Weather (e.g., Fog, clouds, and smoke.)
8. Terrain may hide the objects that the hiker wants to sight with the compass.

The hiker does have control over the following.

1. Purchasing a quality compass such as the Silva Ranger.
2. Correctly adjusting for declination.
3. Staying away from iron and steel objects such as a car, high tension power lines and a hunting rifle.
4. Practiced sighting techniques.
5. Practiced with the procedures of plotting the various lines of bearing.

Blake Miller/Outdoor Quest Image

 The image above closely represents what the hiker will have to deal with and accept.  The crossed lines of bearing provide a rough approximation of a position plotted on the map.

Terrain Association will further "dial in" the hiker's backcountry position.

Blake Miller/Outdoor Quest Image

The image above represents the error of the plotted lines of bearing.  Notice that the lines of bearing have poor angular separation. But by using terrain association the hiker might be able to refine the position fix.  If the hiker is near the river and on the on the river's east side then the position close the road  will better define location.

Navigation is not hard but it does take practice; it is a perishable skill.

When in the wilderness compare both map and compass with a GPS when possible.  Hiking companions should compare their work too.

Read other compass related posts:

     Buying a Magnetic Compass

     Declination

A solid reference is June Fleming's Staying Found and Bjorn Hjellstrom's Be Expert With Map and Compass.

Trouble Shooting Your GPS

What do you do when a compass breaks or the GPS just doesn’t seem to be working right?  Here are a few suggestions that will help the navigator.

The theme of this post is to discuss what options the backcountry navigator has with equipment that might not be working correctly. 

When equipment does not appear to provide the correct indication (such as the GPS bearing to the trail head) it’s time to stop.  Never rush navigation.  Stop and take the time to really look over the information provided.  Consult with the rest of the group.

Being able to recognize the proper operation of the hiker’s equipment is important.  This is obtained through field checks well before any trip.  The gas stove can be tested at home before the journey.  The navigation kit can be evaluated throughout the year at the local park or forest. I recommend to the elk and deer hunters in my GPS classes to take their receiver everywhere they go for two weeks prior to leaving for camp.  Push buttons, change displays, mark a waypoint and finally, return to a destination.  Like a pilot of a plane, a map, compass and GPS are the instruments in the backcountry cockpit.

Normally a magnetic compass’ needle rotates freely.  The needle rotates on a jeweled pivot point.  The magnetic compass should be kept level while in use allowing the magnetic needle to move about in the compasses housing.  My Suunto recently just stopped rotating.  I would change direction about 30 degrees and the magnetic needle would move about 15 degrees and then just hang up.

Sadly, there is no simple in the field fix for this.  I gently tapped the compass body and checked the movement of the housing but nothing seemed to work.  Never let broken gear clutter your pack or be used mistakenly.

A back up compass is very helpful in such a situation.  It doesn’t have to be expensive, just reliable.  No matter what you use for a back up, it has to work well and requires testing.  I take all my new compasses to a location in town where the streets run north and south (degrees true.)  I will hike the streets insuring that the compass is on the mark.  This only takes a few minutes.  Recently I noticed that one of my small ball compasses seemed to be at least 20 degrees off; it’s a goner.  Note, that a small back up compass may not be as precise as your primary model.  Also recognize that some compass will only provide a trend of direction such as moving in a northerly direction as opposed to tracking on a direction of 025°.

Before throwing a quality compass out, contact the manufacturer to see what the warrantee offers.

So what does the hiker do if the GPS receiver appears to be broken?   .

The following are steps that I’ll perform:

1.    If I have a GPS with an electronic compass I’ll ensure the compass is activated.  For example on the Garmin 60 series, pressing and holding the “page” button will turn the compass on or off.

2.    I’ll ensure the electronic compass is calibrated.  The compass must be calibrated after each battery change.

3.    Check the charge on the batteries.  If in doubt replace them.

4.    When the “Go To, Find or Where Is” option has been selected, older models will require motion to cause the compass arrow and displays to adjust.  Take five or more steps and see if there are any changes with the display.

5.    Turn the GPS receiver off, open the battery case and remove one battery for about twenty seconds, return the battery and power up the receiver again. 

6.    Once powered up, I want to be certain that the receiver has captured the signals from at least four satellites.

7.    Worse case - call the manufacturer.  Call early in the morning.

In the field, I leave my receiver powered on, collecting data the entire trip.  I keep my receiver in a holster that attaches to one of my shoulder straps.  Before leaving the trail head I “dump the junk” and get rid of old waypoints (e.g., last year’s fishing trip hot spots), I reset data fields on the odometer page and I will clear out my track log.  As I hike, my receiver is collecting all my trail data.  Should my receiver’s compass display fail I can follow my track (the “bread crumb trail” on the map page) back to the trail head.

Lastly, I will consult my map. Using the major land features (e.g., ridge lines, peaks, etc.) I will orient the map, determine my location (using terrain association) and direction of travel.

Baselayer Clothing

In late November 2013 my local newspaper, the Bend Bulletin (Bend, Oregon) published a supplementary insert called the High Desert Pulse.  On page 28 there was a superb article by Elise Gross titled “Cover Your Bases.”

A base layer is the garment worn closest to the skin.  In the past, most outdoorsmen thought of a base layer as a simple set of “long johns.”  The days of cotton long johns are fading.  Cotton clothing retains moisture and in winter provides no insulation when wet. 

 Ms. Gross provided a fine discussion of the options of the various base layer choices available to the hiker.

She states:

“.. Your activity level and the temperature should be taken into account when choosing a base layer.”

“Fabric type should also be considered.  Base layers are made of a variety of fabrics with unique properties.”

The following is a brief synopsis of what is available.

·         Wool - Merino wool is at the top of my list.  Merino is soft and doesn’t irritate the skin.  Smart Wool is my favorite.  Wool works well in mild to cold temps.  Wool wicks sweat away from the skin.  It dries relatively quickly.  Wool is antibacterial so it doesn’t start to smell over time as silk and poly does.  It’s expensive.

·         Silk – Silk that has been modified to improve wicking is a fine choice (untreated silk absorbs and retains moisture).  Silk works well during periods of heavy physical exertion.  Though it can get too warm, silk works well in cold climates.  Silk takes longer to dry than wool or polyester.  Silk can get stinky so launder after use.

·         Synthetics – These are popular big sellers and big advertisers in outdoor magazines (e.g., Under Amour).  Synthetics are fine in moderate temperatures.  Wet material close to the skin may be chilly until dry.  Moisture wicking is excellent; that’s the big plus.  Synthetics dry faster than any other base layer material.  Synthetics can get stinky so launder after each use.  

All products mentioned are light and take up little space.

Consider carrying an extra top to keep the hiker dry and warm. 

Buying a GPS After The Holidays

The post Holiday Season is a great time to start looking for a new GPS.  There will be sales over the next few weeks.  Manufactures are offering discounts and coupons can be found on line.  Search the Internet for sales promotions and the ads in the Sunday paper.  I will occasionally use www.walmart.com to establish a price baseline.  Take a look at www.gpscity.com too.

Be careful when using “Craig's List.”

Some models with good discounts could very well be out of production units and discontinued.  Evaluate what your needs are and if the price is right and the receiver fits all your requirements, then you are set.

One web site to take a look at is www.GPStracklog.com.  GPStracklog.com is packed with information on what’s new and happening in the world of GPS.  Importantly, at the top of the page, click on “buyers guide” and then select the category that fits your requirements (e.g., auto, outdoors, etc.)

I think the recommendations provided are spot on the mark.

What would I avoid? I am very cautious when buying used GPS or one that has been refurbished.

I want a model that allows me to:

·         Enter many waypoints

·         Edit waypoints

·         Manually enter waypoints (example: your friend provides you the coordinates to a wonderful place next to a bubbling broke for a camping site)

·         Many map datum selection options

·         Will accept topographic maps.

·         Those with less steady hands might consider are receiver with buttons on the front.  Test this in the store or borrow a friend’s.  Ditto for touch screen models.

·         Up load and download GPS waypoints and track data.

Good luck in your search for that new GPS!!