Category Archives: Handheld GPS

Latitude and longitude 2

In the first discussion of latitude and longitude, we investigated how the latitude-longitude grid was established. In this post we will look at how that relates to the display on your handheld GPS unit.

If I stand outside with my GPS and direct the unit to display my position, it may do so in a couple of different ways. First, it might show my position on a map background, pinpointing my location with regard to other features such as streets, buildings, or landforms. This shows me my location as if I were walking around on the map.

I might want to know my latitude and longitude coordinates. Perhaps I want to record them so I can return to this spot in the future. (You can understand why a “bone digger” would want that!) In most handheld GPS units you can save your location as a waypoint. (See my review of the best GPS units.)

A really useful thing to be aware of about has to do with the format of latitude and longitude number displays. These numbers can be expressed in several ways, and you must know which format the numbers are in or risk making errors. After GPS units first came out, I used one to locate some fossil sites where I collected. I happily recorded the coordinates for the fossils I picked up, and dutifully wrote them in my field book. Only later did I realize that I was not perfectly clear which form the coordinates were in, making the records almost useless!

Most handheld GPS units allow you to display the coordinates in several formats. You could show the form degrees-minutes-seconds, sometimes denoted as DMS. This might look something like 38°53’22.49″N, 99°17’58.73″W. Latitude is given as degrees north or south from the equator, and longitude is given as degrees east or west from the prime meridian.

But we could also give these same numbers in another format which would look like: 38° 53.375’N, 99° 17.979’W. This format is in the form of degrees, minutes, and decimal minutes, or DMM.

Finally, we could show these coordinates as full decimal degrees (DDD) and it would look like: 38.889583°, -99.299650°. Note that in this form, the positive or negative form of the number is important as that gives the direction. Positive latitude numbers are north, and negative longitude numbers are west.

Notice that these forms are all equal: 1° 30′ 30″ (DMS); 1° 30.5′ (DMM); 1.5083° (DDD). And you can see if you just wrote down numbers on a page, and were not very clear about which form the numbers were in, you could be very far off the mark in terms of location.

There is another common coordinate form called UTM which we will examine in another post. Bonus points to anyone who can tell me what is at the coordinates used in this post.

Latitude & Longitude

Thought question: when you are standing at the North Pole, which direction are you looking?

A topic that I think people find a bit confusing is the coordinate systems commonly used in their handheld GPS units. The handheld GPS can tell you your exact location, and this is because cartographers have partitioned the surface of the Earth so that one point can be located with regard to any other point. However, over time they have developed a variety of different coordinate systems to meet various needs.

The most commonly used coordinate system is probably the latitude and longitude grid. This system is based on two 360 degree circles that are envisioned to circle the planet. The first great circle spans the planet from “head to toe,” or along the axis of rotation. The second great circle goes around the “waist” of the planet, at right angles to the axis of rotation, and along the planet’s midline. We call this great circle the equator.

You no doubt learned that a circle can be divided into 360 degrees. The circle of the equator can likewise be divided, but where should we start? The line projected from the North Pole through Greenwich, England, through the equator to the South Pole is the prime meridian. Here, “prime” means “first” or “initial.” The point where it crosses the equator is the starting point for dividing the equatorial circle.

Why Greenwich, England, you ask? This standard was really only recently set, in 1884, when delegates from 25 nations met in Washington, D.C. for the International Meridian Conference. They adopted the meridian passing through the Transit Instrument at the Greenwich Observatory as the “prime” one. You have to start somewhere!

From the prime meridian, we can measure around the circle of the equator east and west up to 180 degrees, covering the full circle. This establishes the lines of longitude (running from the pole to pole) and defines the directions “east” and “west.”

We can divide the prime meridian into its 360 degrees also, and we find it useful to start at the equator and count 180 degrees from pole to pole. So, you can go from zero to 90 degrees in both directions, north and south, and this establishes lines of latitude, and defines “north” and “south.”

Notice that lines of latitude do not converge on a spot—they remain parallel to each other on the globe. However, lines of longitude do converge, at the poles. What this means is that the distance on the ground remains the same between degrees of latitude. But the degrees of longitude get closer together as you approach the poles. In other words, one degree of longitude at the equator is a longer physical distance on the ground than one degree of longitude farther to the north, say in Greenland. This is just an interesting complication of living on a sphere.

And it is because of that complication that I know exactly which direction you are looking when you are standing on the North Pole—no matter how you turn your body, you are by definition looking south. At 90 degrees north there is so other way to go but down (in latitude, that is).

Geocaching

Do you enjoy hiking and exploring the outdoors, seeing new places, and having fun? Maybe you want to try geocaching.

Geocaching (pronounced geo-cashing) has fast become a popular pastime for outdoor adventurers, especially those who use a handheld GPS. Basically, geocaching is a grown-up version of hide and seek. Someone places a “surprise” package, or cache, and provides its latitude and longitude coordinates to others who then try and find it again.

This activity is enjoyed by people from all walks of life, young and old, and is great fun. There is a hint of the exotic to the hobby, making you feel like Indiana Jones seeking out lost and hidden treasure.

The cache is usually stored in a water-tight container to protect it from the elements, and often contains a log for visitors to sign. Sometimes there are trinkets to be found too. Caching etiquette dictates that you are welcome to take one of the trinkets, but you must leave something in return.

Maybe the cache hider will leave a disposable camera for example, and request that visitors take a picture of themselves and return the camera to the box. This way there is a fun record of who all has braved the elements and sleuthed out the cache’s location.

You can find the locations of geocaches near you, or near where you want to explore, through web sites like geocaching.com. A basic membership there is free and gives you access to the locations of geocaches and allows you to share your adventures with others.

If you really get into this hobby, maybe you would like to create a geocache for others to find. There are guidelines that should be followed as the goal is to have a safe and fun experience while protecting the environment around the cache. First, be sure you have the permission of the landowner or manager. If people are going to be visiting the area looking for your geocache, they don’t want to be chased off by a surprised and angry landowner.

You need to hide your cache were it is unlikely to be found by a casual visitor, and in such a way that getting to it will not harm the local resources. You should leave a log and a writing utensil, preferably a soft lead pencil if the area will get below freezing. Also, leave a note for the hunters, explaining why the location is important to you, and explaining the basic idea of the game for someone who does stumble upon the site accidentally. Obviously, do not leave food or anything dangerous or illegal.

A good handheld GPS is critical for this activity as it is based upon recovering the coordinates of the geocache. You can find information about GPS units, basics of their features, and recommendations on models to purchase here at boneblogger.

Check back here often because we will be posting more about this fun outdoor activity. Have fun, and be safe everyone.

Recommended handheld GPS units

If you are just finding this post, you may wish to review the previous posts on what GPS is and some of the most common features to consider when thinking of buying a handheld GPS.

When it comes to rating, Garmin handheld GPS units consistently rank highly among users, and they have a wide range of models and prices.

For the price, the Garmin eTrex Venture HC GPS Receiver is well recommended. This unit retails for around $100, so it is not the least expensive model, but comes with enough features to make spending a little bit more worth it.

Garmin eTrex Venture HC

The screen is 1.3 x 1.7 inches and is color. The unit weighs 5.5 ounces so it is not too taxing to carry, and runs on 2 AA batteries. The battery life is rated at 14 hours of use; not too bad. It is waterproof, and has a 24 MB built-in memory. It can store 500 waypoints, and 50 routes, plenty enough for the average user.

Reviewers report that this unit can hold its satellite signal even with tree and cloud coverage, an important feature for many hikers. And it easily connects to your computer for transferring data, including additional detailed maps. The additional map sets are not inexpensive, however, but I have found them to be very useful for trekking in the wild.

It does not have a digital compass, but will show the direction you need to travel to the next waypoint as an arrow on a compass dial only when you are moving.

If you are a bit more adventurous (and willing to spend more) the Garmin Oregon 200 may be for you. This model retails for $230-370, and has a lot more features to play with.

Garmin Oregon 200

It has a large (1.5 x 2.5 inch) color, touch screen. Since the controls are on the touch screen, the buttons can be larger and easier to see than non-touch screen models. However, touch screens can take a bit to get used to.

View of the Oregon 200 touch screen

It is waterproof, and heavier than the Venture model, weighing in at 6.8 ounces. The Oregon battery life runs 16 hours on 2 AAs. Like the Venture, the Oregon has 24 MB of built-in memory, but unlike it, the Oregon accepts microSD cards, increasing your memory capacity many times. Also unlike the Venture, the Oregon’s built in map has topography detail.

One reviewer mentioned the weight of the Oregon as being noticeable, but the case is built ruggedly and seems substantial.

Looking for a few more features? The Oregon 400 series features units that are set up for specific outdoor activities like the 400c that focuses on coastal waterways, the 400i that focuses on inland waterways, and the 400t that is for hiking and biking. You pay more for this series as they include more maps pre-installed. Near as I can tell the maps are comparable with the 1:100,000 scale topographic series, and so they may not be detailed enough for the very serious hiker. I think I would save the money and use the price difference to purchase better quality 1:24,000 scale maps, for example, but if you don’t need that much map detail, the 400 series might be the way to go.

The Garmin Oregon 450 series is the next step up in memory and features. There is an Oregon 300 series, but for the same price range they have the 450 series, with more memory and a tilt compensating compass. The 550 series includes a digital camera with the unit so you can take georeferenced pictures.

At this time, the “sweet spot” for features and price for the average or even advanced user seems to balance around the Oregon 200 or 450. The eTrex is also recommended for those on more of a budget. These handheld GPS units balance the considerations of cost verses features well and offer two different price points for you to consider.

Basic features in a handheld GPS

In the basic post on GPS, we explored what GPS was and urged that you consider your needs for a handheld GPS before buying one. There are many features available on the various models out there, and there may be some features you would like, and likely some you would never use.

Screens

But before we get into the more exotic features, let’s look at the basics. One of the most important and basic features of any GPS is its screen. The screens on handheld units are basically of two flavors—monochrome and full color. As you would expect, the color screens are a premium feature and add to the cost. Screen size is also a significant consideration. A small screen can be very hard to see, and even if it looks OK in a store, taking it out into bright sunlight can really change a screen’s visibility.

Unit Size

Overall size and weight of the GPS unit are also something to consider. If you are planning to carry the unit around on hikes, small is definitely better. If it is so large and heavy that it gets left behind, it does you little good. It might not seem like it, but every ounce counts when lugging it around all day. On the other hand, if you are mounting it to your bike or boat, or driving into remote areas, its overall size might be less of a limiting factor.

Data handling

Be sure to review the unit’s ability to store waypoints and routes. A waypoint is simply the coordinates of any point you would like to reference again. For example, you might want to mark your car, camp, or house as a waypoint. It is fun when you are out in the boonies to see the direction and distance back to the house (“Look, we are 454 miles from home!”). Most units allow you to store several hundred to a thousand or more points.

A route is a series of connected waypoints that moves you from a beginning point to a destination. For example, on a hike you might start at the trail head, travel to a junction with another trail, take the right fork, and end at your camp. The route on the GPS will direct you from point to point as you go.

Some GPS units will allow you to save tracks. This is like leaving digital breadcrumbs. As you travel, the unit will mark your path along the way, showing where you have been.

Some of the GPS units allow you to connect them to a computer and move information back and forth between them. This is really handy in a number of ways. You could plan your route at home on the computer, upload the route to the GPS and let it take you on your way. Or, you might like to wander off and blaze your own trail, then download the track record to your computer to save a record of where you went.

Another important information-sharing feature is being able to upload additional maps into the handheld GPS unit. Most come with pre-installed maps, but depending on the unit, its maps might be more appropriate for a day hiking the golf course than trekking through seldom-explored wilderness. You can purchase software and map sets to load into your GPS so you could have full map details of the region you are planning to visit while in the field. You can also get free maps for Garmin GPS units at GPSFileDepot.

Weather resistance

Units might be billed as water proof or water resistant. Water resistant means that the unit can handle being splashed with water. Water proof means the unit can take being fully submerged in the creek or lake. Clearly, if you are going to be out in inclement weather, water proof is going to be an important feature. However, water proof does not mean you should plan to swim with it.

Signal receiving

Units vary as to how well they can receive the signals from the satellites. More expensive models often feature better signal capabilities that allows them to provide your location through trees and other sky-coverage. If you are going to be using your unit to travel in remote regions, make sure to get a high sensitivity receiver. You can also explore getting one with Wide Area Augmentation System (WAAS). This system supplements the standard GPS satellite system and provides for increased accuracy. It is not available everywhere, but if the unit you have is capable of receiving the WAAS signals, it will at no extra cost, and will increase the accuracy of your locations up to five times.

Battery life

Finally, you might consider battery life and type. Most units run on disposable batteries, typically AA, but they do not all consume batteries at the same rate. Some units have AC adapters, and some do not. Some have an internal rechargeable battery. Each style has trade offs. For example the disposable battery option might be fine for use a few times a year, but if you are a regular adventurer, you could spend a lot of money on batteries in a season.

Those are some of the basic features to consider. In future posts we will look at some of the fancier features, and investigate specific models.

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