The venerable Garmin GPSMAP 76Csx has been around for a few years now but is still an excellent GPS to use for geocaching. The Csx refers to C for Colour screen, s for Sensor (compass and altimeter) and x for micro-SD card.
Important features for geocaching include:
- Sensitive GPS receiver
- Electronic compass
- Bright colour TFT screen -readable in any light
- Ability to upload maps
- Micro-SD card for storing waypoints and maps
- Ability to store 1000 waypoints
- Rugged and waterproof
The circuitry in the 76Csx is identical to the 60Csx and therefore they are functionally the same.
It uses the SiRFstarIII chipset which are the receiver and processing chips that receive the signals from the GPS satellites, calculate the co-ordinates and run the software in the unit.
It means that the unit is more sensitive under tree canopy and in urban (or natural) canyons. In difficult environments like these the GPS will receive both direct and reflected signals that bounce off hard surfaces and cause multipath reflections. This introduces errors into the process and is why you have trouble locating caches in these sort of conditions.
The SiRFstar III chipset has the processing power to crunch the numbers from all the reflected signals and come up with something meaningful. This processing power also means that the chipset can consider weak signals that were ignored by previous chipsets. The SiRFstar III also has faster acquisition times, making for a faster time to first fix (TTFF), and a quicker reacquisition if the signal is lost.
Geocaching is often about trying to locate a container within a small radius. So often we are under trees or in between buildings, and it's in situations like these that the excellent reception of the 76Csx comes in handy. This sensitivity is just as important when placing a cache. In addition the 76Csx has the ability average co-ordinates to improve the accuracy of placement even more. I have placed many caches using this unit and finders report very accurate co-ordinates even in difficult locations.
Garmin claims a battery life of about 30 hours using normal alkaline batteries. I used rechargeable 2700 mAh batteries and although I never actually timed hours of operation I am able to do several geocaching runs over a number of days on the same batteries.
The 76Csx comes with a base map of whichever country you bought it. However you can upload other maps that take priority over the basemap. In fact you can upload a number of maps via the USB port and select which one is displayed.
It comes with Mapsource which enables you to upload various maps and waypoints.
Using the GPSMAP 76Csx
The unit has the typical Garmin interface and buttons. It has 6 main pages; Satellite page, Trip computer page, Map page, Compass page, Altimeter page and the main menu. You cycle through the pages by pressing the MENU button to go forward and the QUIT button to go in reverse. Extra pages can be added in page sequence option of the main menu.
The 76Csx is "geocache ready" which means that it has a two waypoint symbols; one for "Unfound" cache and the other for "Found" caches. It also has a calendar feature that shows when you found the caches. There is also a search feature for geocaches that is separate from normal waypoint searches.
I use the GSAK Smart Tag feature to create meaningful waypoint codes that indicate type of cache (traditional, multi etc.), container size, terrain, difficulty and text for the hint. This appears on the compass page under Notes. An annoying feature of the Compass page is that it is too easy to hit the Found button and remove the cache from the list of unfound caches. If you do accidentally hit the Found button, you have to find that cache in the list of waypoints and change the symbol back to an unfound cache.
The nice thing about having an electronic compass is that it will point to the cache even when you standing still. When using GPS units that don't have this feature you have to be moving before the needle will point to where you need to go.
However it is important to calibrate the compass. If you don't calibrate the needle will point in the wrong direction when you trying to find a cache. To calibrate, go to the Compass page, hitting menu and selecting Calibrate. When you select Start you turn at a certain speed until the unit tells you it has finished.
As is typical of Garmin units it is rugged and waterproof. In fact it is rated to IPx7 (Ingress Protection rating), which means that you can submerse it in water to a depth of 1m for up to 30 minutes. The backside of the unit has rubber covers for the battery case, antenna and power connectors.
A handy feature if you're canoeing or boating is that it floats. I don't know how they build it so light. The newer Oregons and Colorados are much heavy and would sink like a stone if dropped them overboard.
It certainly is rugged. I was using it to navigate while flying my hang glider. It had a nasty whack when I had a "non-optimal" landing but like a Timex watch, it took a lickin' and kept on tickin'.
The Garmin GPSMAP 76Csx is an excellent unit for geocaching because it has high sensitivity, a colour screen that is readable in any light, an electronic compass and a number of specific geocaching features. In addition it is rugged and waterproof so that it will handle any conditions that in which you may be working.
Because it is now over five years old, you can pick them up for a few hundred dollars. If I had the choice I would recommend one of these over something like an e-Trex if you could pick it up for the similar money. I would also choose a 76Csx over a 60Csx because of ability to float and be used as a marine GPS.
In summary, the Garmin GPSMAP 76Csx is an excellent unit for geocaching. It's an oldie but a goodie.
A GPS unit is the primary tool for geocachers so it's important to have a really good understanding of how the system works, the limitations and things to consider when using them. A good working knowledge of the system will help you to understand how to geocache properly.
The GPS system is one of the great inventions of the 20th century. It has revolutionized navigation and many applications have been developed that make use of this system.
The system that we use for geocaching is called GNSS, or Global Navigation Satellite System. It was set up and is operated by the US Air Force and costs billions of dollars. We get to use it for free!
Basically GNSS is based on about 24 satellites that orbit the earth and transmit a radio signal towards the ground. The signals from the satellites are all synchronized to incredible accuracy by a ground-based atomic clock.
The GPS unit that you hold in your hand is basically a radio receiver (not a transmitter!) that is able to calculate the time differences from the signals that it receives from the various satellites that it can "see" in the sky above where you are standing.
Remember that these signals are travelling at the speed of light, so the time differences from the various satellites are minuscule. Even so, your GPS can detect these differences and triangulate where you are down to about 3 metres at best. The optimal place to get the most accurate fix is when you can see clear sky all around, such as on the top of a hill, or out on the water. The signal is degraded if you are, for example, under trees, in a canyon, in amongst tall buildings or anywhere you don't have a clear view of the sky.
The GPS receiver is a marvel of modern technology. To give you an idea of its sensitivity, it is equivalent to trying to see a 100 watt light bulb located 10,988 nautical miles out in space!
So what does this mean for you?
It means that next time you're trying to find a geocache be aware of the limitations in the accuracy of position. The best accuracy your unit can achieve in the most optimal conditions is about 3 metres (~10ft). So your search radius is about 3 metres from where your GPS says is GZ - and that's assuming that the cache owner has published accurate co-ordinates. If you are under trees, in a canyon or some other difficult location, your search radius may be wider.
It also means that when you are placing a cache don't just hide the container, mark the location and leave. That's a recipe for inaccurate co-ordinates. Spend the the time to average the position (a good GPS has this function) to get accurate co-ordinates - especially if it's in a location where the signal is not so good. Your fellow geocachers will have loving thoughts towards you if your co-ords are accurate.
This is a really important subject when you learning how to geocache, so we'll go into more detail elsewhere.
What is the best GPS system to use for geocaching?
The main features to look for include:
- High sensitivity receiver (e.g. SiRF chip set)
- Waterproof (floating optional but useful on a boat)
- Ability to load as many waypoints as possible e.g. 1000 is good
- Inbuilt maps and the ability to upload new maps
- Colour screen
The Truth About GPS: How it works