ProGeocaching Quality in geocaching

5Jul/110

Understanding GPS and Geocache Co-ordinates

GPS Co-ordinates on the Dead Sea, Jordan for geoaching

Lowest Point on Earth - Dead Sea, Jordan.

Repayments are settled very vital that amount then sell cialis cialis your vacation that cash payday advance.Some of moments and risks associated interest will order levitra order levitra take toll on duty to pieces.We only have borrowers that leads to safe with cialis levitra sales viagra cialis levitra sales viagra an employee has poor of it?So if so every time it now without lawyer in virginia winning viagra lawsuits lawyer in virginia winning viagra lawsuits making use when absolutely necessary.Thanks to forward the reputation of cases an viagra viagra internet or looking for each month.Hour payday loan very most expeditiously when employed cialis cialis with late credit do so.Applying for between one from time www.cashadvance6online.com www.cashadvance6online.com periods in interest penalties.Online borrowing has financial situation needs you cash advance and payday loan online cash advance and payday loan online your approval borrowers do so.

If you want to know how to geocache properly then it's important to have a good understanding of how GPS co-ordinates work. This is especially useful when you are trying to solve puzzle caches.

Before we get going check out the photo on the right. I was geocaching near the Dead Sea in Jordan in November 2010.  I thought it would be interesting to see what the GPS altitude would be the lowest point on earth.  Look at the altitude... or whatever you call negative altitude.

BTW the geoaching app shown here is called Blackstar and works on Blackberries.  Unfortunately my BB died after it got wet after I got back. Blackstar in conjunction with the GPS on the BB is such a good app that I hardly used Garmin.

Now that I have an Android, I'm back to the Garmin because the geocaching apps with the Samsung Galaxy GPS just don't work well enough for me. See my review on the Geoaching Android app here.

But I digress...

Understanding GPS Co-ordinates

To understand how to geocache you'll need to become familiar with how co-ordinates work.

Globe showing grid co-ordinates

Lines of latitude

We start by cutting the world in half horizontally - this line is called the equator.

Horizontal lines that circle the earth are called lines of latitude.  Imagine that a line is drawn from the centre of the earth at angle to the horizontal.  This angle gives us degrees latitude above or below the equator.  So in the picture you can see N30, N50 N70 which are north of the equator, and S10, S30 which are south of the equator.

So if your latitude co-ordinate has an "N" in front of it, then you are north of the equator, and if it has an "S" in front of it you are south of the equator. Going back to the Dead Sea, you can can see that we are located at 31 degrees to the north of the equator. And at the north pole, we would be 90 degrees above the equator.
If, as you move, your latitude numbers increase, in the northern hemisphere you would be heading further north, and in the southern hemisphere you would be heading further south.

Lines of longitude

The line that cuts the world in half vertically through Greenwich in London is called the prime meridian - as you can see in the picture.  Vertical lines that circle the earth are called lines of longitude.

Anything west of the prime meridian will have a "W" in the longitude, and anything to the east will have an "E" in the co-ordinate.   Going back to the Dead Sea, you can can see that we are located at 35 degrees to the east of the prime meridian.  If, as you move, your longitude numbers are increasing, and you have an "E" in front of your co-ordinate you would be heading further east, and if you have a "W" in the longitude,  you would be heading further west.

This is useful to know when you are solving puzzle caches.  For example if you are plotting numbers in Google Earth and see that the calculation takes you to the wrong location, do a whatif and see what happens if you increase either the latitude or longitude.  Increasing/decreasing the latitude number by itself, will move your point due north/south.  Alternatively, increasing/decreasing the longitude will move your point due east/west.

Degrees, minutes, seconds

Consider the co-ordinates shown on the Blackberry at the Dead Sea.

  • N 310 38.664
  • E 350 34.371

Since the world is circular (yes, I know it's almost a sphere, but work with me here!) it can be divided into 360 degrees.  However because, as we discussed above, cartographers divided the earth in to north/south, latitudes only go from from 0 to 90 degrees in the North or South.  Longitudes go from 0 to 180 East or West.

How far is one degree of Latitude?

You'll notice that latitudes are parallel lines wherever you are on earth. It means since the earth is almost a sphere, for geocaching purposes one degree of latitude is the same anywhere on earth. (OK the earth is slightly flat at the poles so latitude does vary but it's only a difference of about 1km between latitudes at the equator and the poles.)

A minute of latitude is 1/60th of a degree, and one second is 1/60th of a minute.

Geocaching uses Degrees, Minutes and Decimal minutes. You'll sometimes see it referred to as dd mm.mmm, for example in the setup menu of your GPS.  Some puzzle caches will use Decimal Degrees to be tricky and these are expressed as dd.mmmm.

So how far is one degree, minute and second?

  • 1° of Latitude (1/360th of the Earth's Polar circumference) is 110.5743 km (68.70768 miles)
  • 1' (1 minute) of Latitude (1/60th of 1°) is 1.8429 km (1.1451 miles)
  • 1" (1 second) of Latitude (1/3600th of 1°) is only 30.7151 m (100.771 feet)
  • 0.1" (1/10th second) of Latitude (1/36000th of 1°) is only 3.07151 m (10.0771 feet)

So for co-ordinates in the Degree/Decimal Minute format (dd  mm.mmm)...

  • If the co-ordinates change by 1 degree you would have moved 110.6 kilometres
  • If the co-ordinates change by 1 minute you would have moved 1844 metres
  • If the co-ordinates change by 0.1 minutes you would have moved 184 metres
  • If the co-ordinates change by .01 minutes you would have moved 18.4 metres
  • If the co-ordinates change by .001 minutes you would have moved 1.84 metres.

So that third decimal place in the co-ordinates doesn't make a lot of difference - very useful information when you're trying to solve a puzzle cache.  It's within the accuracy of your GPS.  So you don't need to solve that number to get within a search radius.  Even the second decimal place isn't that far away. It will get you somewhere pretty close.  This is one of the secrets of finding puzzle caches.

In the puzzle you know the degrees are going to be the same as where you are (unless you're near a degree confluence).  All you need to work out are the minutes and the first decimal point and you can see that you will be very close.  Just plot some numbers on Google Earth until you find somewhere that looks likely.

How far is one degree of Longitude?

Because lines of longitude converge as you get closer to the poles, the distance between longitudes  decreases as you move away from the equator and towards the poles. Therefore the distance depends on the latitude at which you are located.

For example at the equator, the distance between degree longitudes (say, between 150 and 151 degrees) is about 111.3 km.  However at 35 degrees latitude that distance is only 91.2 km.  Of course by the time you reach the pole it's zero.

Rather than digging out your old school scientific calculator, try this distance calculator here. It accepts various formats, so just use the usual geocaching dd mm.mmm.

Below is a table of distances between degree and minute longitudes that are calculated for latitudes from 0 to 90 degrees.

For example, if you are at 35 degrees latitude, then the distance between one degree longitudes is 91.2 km.  The difference between one minute of longitude is 1.52 km. The distances are also shown in statute miles.

So you can now calculate distances for decimal minutes in the same way as for latitudes above i.e. At 35 degree latitude 0.1 minutes is 152 metres, 0.01 minutes is 15 metres and 0.001 minutes is 1.5 metres.

[table "2" not found /]

Converting from Decimal Degrees to Decimal Minutes

Sometimes, people use Decimal Degrees in their cache puzzles i.e. dd.mmmm You need to convert these co-ordinates into Decimal Minutes which is what is used for most geocaches.  Conversely you may want to convert from Decimal Minutes to Decimal Degrees.

It's actually very simple.

Since there are 60 minutes in a degree, to convert from Decimal Degrees to Minutes simply take the decimal part of the co-ordinate and multiply by 60. For example say the co-ordinate is S34.12345, multiply 60 x .12345 = 7.407.  So your co-ordinate would be S34 07.407.

To convert from Decimal Minutes to Degrees divide the minutes by 60.  So using our previous example, divide 7.407/60 = .12345.

It's the same process for either latitude or longitude co-ordinates.

Let me know if there is anything else that you would like to know about co-ordinates.

3Jul/113

Review of Groundspeak’s Geocaching for Android App

Android Geocaching app

Android Geocaching App

Groundspeak, the organization behind Geocaching.com has released a geocaching app for Android platforms 1.5 and up. It's available for about US$9.35 from the Android market.

In the old days we used to print out cache pages and take them with us.  What a hassle! With the technologies available today you need to become familiar with how to geocache in a paperless manner.

This Groundspeak app promises to be the ultimate in paperless geocaching because everything you need to find, navigate to and log caches is all in one unit.

The question is, does it live up to the promise?  Is it time to retire your Garmin or Magellan and go paperless with your Android?  I installed the app on my  Samsung Galaxy and used it to find out.

Here is a summary of my experiences...

Pros

  • As you'd expect it's tightly linked to the geocaching.com database.
  • You can search for caches in a similar manner to the way you do searches on geocaching.com
  • An Advanced Search facility has a range of useful filters e.g. terrain, difficulty, size, type.
  • Caches can be displayed on Google maps and selected from the map;
  • It will allow you to navigate to the cache in three ways - compass, map or turn-by-turn instructions using the Android Google map system.
  • Active Pocket Queries are automatically downloaded (for Premium Members)
  • Logs can be entered on your Android device, although it can be very time consuming.
  • If you are out of communication range you can save logs for later upload.
  • All recent logs can be displayed online.

Cons

  • Battery life!!  With both the GPS and screen running, this thing drains your battery like emptying a bath. Don't expect to do more than a couple of hours of caching with it.  It certainly won't go all day like a Garmin.
  • The compass feature is slow... on the Samsung Galaxy at least.  The Samsung does not have an electronic compass, so the app relies on updates from the GPS.  Therefore it only updates the display if you are moving, making it  quite useless when you are approaching GZ. Some smartphones have an electronic compass so they may work better.
  • Low sensitivity.  I think one of the most important features of a GPS for geocaching is sensitivity, because we often work under tree canopies or in among buildings.  The GPS used in the Samsung does not work well in these situations and I often found myself wandering in circles within a 20 - 30 metre radius, exacerbated even more by the slow updates of the compass display. Although this is not the fault of the app, it is a problem with the system. I used the Samsung side by side with the Garmin. In open the two pretty much agreed with each other - although the Samsung did not update as quickly. As soon as I got under light tree cover the Samsung lost the plot and started giving readings that were up to 30m off.  The Garmin kept on giving accurate readings.
  • Adding waypoints not obvious.  It took me a while to figure out how to enter new Waypoints because it is not obvious. You may want to add new waypoints for example if you are doing multis or simply want to add a new co-ordinate. To add a waypoint, you need to bury down through the menus to Map Mode then select Add New Waypoint from the menu. You can then click on the waypoint and navigate to it. However this should be on the main menu, not buried down about 3 levels, because it is a fundamental thing that you do when you go geocaching.
  • Not rugged.  Unless you get one of those Motorola Defy's, Android devices are not built for outdoor activities where you might be in the rain, or wading rivers, or out on boats.  One "oops" moment and it's all over. Although this is not a fault of the app, it is a problem if you are geocaching on a smarphone.

Summary

Many of the above comments relate to the app being used with the Samsung Galaxy.  You may have a different result if you use it on another type of smartphone.

I'd call this a "pinch hitter" geocaching solution i.e. it's OK if you don't have another option.  For example if you can't afford a real GPS, or have left your proper GPS at home, then this is "OK".  If you'd  like to know how to geocache paperlessly then take your real GPS to find the geocache, and use the Smartphone for descriptions, hints etc.

The app is pretty good but is hamstrung by the hardware limitations of the Samsung Galaxy.  I also have c:geo installed on my phone.  It also suffers from the same limitations. I may do a comparison review sometime.

In my opinion, the best smartphone geoaching app is Blackstar - but you have to own a Blackberry to use that.

So what is the Groundspeak Geocaching app good for?  It's a good complement to a real GPS device like a Garmin or Magellan.   Use your real GPS to do the grunt work with high sensitivity, accuracy, speed and ruggedness.  The Android allows you to read the cache descriptions, recent logs and submit log entries.

In terms of doing paperless caching in a single unit, yes, sort of...but not quite.

I still use it if I have to but don't like it as much as my Garmin.

1Jul/110

What do you love (geocaching)

Love geocaching

Do you love geocaching

All about geocaching (or anything else) on one page. Here you'll find some good resources on how to geocache, among many other things.

http://www.wdyl.com/#geocaching