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Converting Lat Lon data

Old 09-28-2008, 09:50 PM
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Default Converting Lat Lon data

Is there an easy way to convert Lat Lon data to another format, either DDD.dddddd or DD.MM.mmmm?

Here is an example of the numbers I would like to convert

31 43.009N
080 40.188W

Thanks.
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Old 09-28-2008, 09:55 PM
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Default Re: Converting Lat Lon data

Easiest way is to install GPS software like Garmin's Mapsource, or the free ones around the web (EASYGPS, GPS Utility...), enter the location in as a waypoint, then go to the settings, and change the lat/long format the program displays. Now open the waypint agian and it is now converted.
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Old 09-29-2008, 03:37 AM
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Default Re: Converting Lat Lon data

It looks like the example you posted is already in the form DD mm.mmm.

I am unaware of a DD.dddddd format. Degrees and decimal places of degrees? But if you really wanted to convert say 080 40.188W to degrees.degrees degrees then you would simply DIVIDE 40.188 by 60 - as there are 60 minutes in one degree. So in DD.ddddd format 080 40.188 would be 080.6698W.

To convert from DD.ddddd to DD mm.mmm MULTIPLY the decimal numbers by 60. So 080.6698 becomes 080 40.188 again.

To convert from DD mm ss (degrees minutes seconds) to DD mm.mmm DIVIDE the seconds by 6, then move the decimal one place to the left. So 54 seconds becomes .9 minutes (54/6 = 9, move decimal place over one place to the left and you get .9)

One second becomes .0166666666666...... minutes. The conversion is not perfect because of a repeating decimal, so at some point you have to round up a digit to 7 or else you have an infinite series of repeating 6s. Which nobody really likes - except for people way too into number theory. But if you ask me, by the time you are in the hundred millionth place, go ahead and round that place number up to 7 and call it quitting time.

080 45m 28s becomes 080 45.467 (rounding the last place up - but by the time you get down to one thousandth of a minute you are only talking about 6 feet anyway).

To convert from tenths of a minute to seconds, multiply the decimal numbers by 6, then move the decimal over one place to the right. Doing so means 31 43.009N converts to 31d 43m .54s (actually 31d 43m 01s as you do not usually deal with fractions if you are displaying coordinates in dd mm ss - so I would just round up and call it good). Once again, rounding up from .54 seconds to 1 second is only about 6 feet - so not a whole lot of difference there either.

1/100 of a second works out to about 1 foot by the way - 6072 feet in 1 nautical mile, divided by 60 gives you seconds (101.2) divided by 100 gives you 1.012 feet.

Unless of course, my math is wrong. I do not think it is but anything is possible. Lord knows, my math has been REALLY wrong in the past!

It probably is easier to just use a computer program to convert the data. Or you can probably use whatever format you have, and enter the data into the GPS itself - setting the GPS to accept data in the format you have of course. Then let the GPS deal with the conversion math.
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Old 09-29-2008, 09:23 PM
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Default RE: Converting Lat Lon data

Thanks for the replies. I figured out that you need to add an extra zero on the end of the numbers and then it works. The Furuno NavNet3d needs the extra 0.
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Old 09-30-2008, 03:21 AM
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Default Re: Converting Lat Lon data

excell will do it you tell it to.
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Old 09-30-2008, 07:01 PM
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Default Re: Converting Lat Lon data

Just got off the phone with Carl Andren from Andren Software. His LoranGPS product is supposed to be the "stuff" and is the only one supposedly that converts loran to gps with any real accuracy. While at the Fishing show this weekend, many people asked about converting loran numbers to GPS and that's really the only one in the industry that I've heard of for many years. Just an opinion for what it's worth.

You can order it on his site or I can get anyone a copy of version 7 that wants it.


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Old 10-01-2008, 01:18 PM
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Default Re: Converting Lat Lon data

Huh? There is tons of software products that will convert Loran to GPS.

What doe the one yur referring to run on?
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Old 10-01-2008, 01:59 PM
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Default Re: Converting Lat Lon data

You may want to research that. Yes there are a lot of software that converts loran to GPS, but there are a lot of factors involved that relates to the accuracy of the conversion. Not sticking up for Andren, but from the research I have done, it seems to be the most accurate when used correctly and you calibrate it with known spots in your area. Known being several spots that you have not only the loran number to, but also the GPS number to. That coupled with several can calibrate the software to provide better accuracy. Read the details of some of the software vendors, most are full of disclaimers and warnings. If it were an exact science and an a easy accurate conversion, you wouldn't have people with hundreds of loran numbers they can't do anything with..... good luck on this one.
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Old 10-01-2008, 04:31 PM
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Default Re: Converting Lat Lon data

I've been using andrew loran software for many years. Great program and is the only way to convert accurately. But you have to read the manaul and do the conversion by the book. My test have it to within about 100 ft. My old NS was good to 300' on a good day.
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Old 10-02-2008, 03:53 AM
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Default Re: Converting Lat Lon data

There is no software that alone will convert Loran to equiv GPS accuracy. There are ways and means that this can be done but software alone won't do it.

100' is certainly a lot better than 300 feet but even 100 feet is about 3 times that of equiv GPS world wide accuracy.
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Old 10-02-2008, 04:46 AM
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Default Re: Converting Lat Lon data

How do you think the GPS does it? The GPS does not have the capabilty to receive loran signals, its not a loran receiver. The answer is the built in software in the GPS.

You are totally correct that software alone cannot do it. A GPS unit also cannot do alone either. You need both a GPS and Loran Receiver to get lat/longs and loran td's taken at the same exact location. Then the software can be "Calibrated" with good data. This is only way to convert a td to lat/long with some degree of accuarcy. It is mathematically impossible otherwise.

The Andrews Loran Program takes loran c (td's) and gps data (lat/longs) taken from a few locations (they have to be taken at the same location) and converts the loran to a lat/long using a very powerful algorithm; software that is too big for any GPS unit. GPS units cannot do this. Once you calibrated for a region, you're set and can convert all the td's in THAT region. Change your region and you to have re-calibrate. Trust me, it works.

Its explained here:

http://www.andren.com/

I've spend a lot of time on this because I have a lot of good numbers that I could not lose.

We may be talking about differnent things here. Hope on I'm clear on this. GPS units will get to within 15' or so. Using a converted Lat/long in a gps will get you to you to within 100'. Using a td in a GPS may get you within a mile or so (i've been off up to 5 miles). The old NS 941/952 would do much better and is best GPS for converting tds. Not so, for the newer NS's. This differences are a function of the mathematics (and curvature of the earth) and not the loran/gps recievers.

I have no interest in this program, this is not a sales pitch.



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Old 10-08-2008, 02:59 AM
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Default Re: Converting Lat Lon data

So true as a GPS and Loran are totally totally different beasts. This is one of the problems with calibrating Loran for a particular area as even the difference between high and low water especially when the signal travels ober land can make quite a bit of difference.

The wider the "region" then the more suspect is the conversion. This is one thing that people need to understand in that they simply can not convert TD's with any degree of accurayc without first going out and collecting ACTUAL differences over the rea of interest.

....but even 100 feet is about 3 times that of equiv GPS world wide accuracy.
Just to clarify myself, within the past month the new GPS accuracy spec now changes the "3 times" to about 6 times!
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