GPS vs topo, old and new?

[BMWST?]

ok i hope somene can help here.At one time I bought a R100 gs and was looking at an old Topo map,for roads routes .Then i had an idea to place the NI tag o rama at an intersection using map references.I thought map references were literal long lats but maybe not?I also found that NZ has a new mapping/survey? system which further confuses me.
So the question to the gurus is,if i place a map reference from a 1996 1:50,000 Topo map is this something that can be used by an owner of a newer series topomap or a gps? For example a certain establishment has a topo map reference of r28,r27&ptQ27 893770,and i will meet you there for lunch.Where am i going to meet you?

[NordieBoy]

For example a certain establishment has a topo map reference of r28,r27&ptQ27 893770,and i will meet you there for lunch.Where am i going to meet you?

I'm going to meet you at Ambrosia in Richmond.
You may not turn up though.

By the way, you're paying :D


Those numbers have no meaning for me at all.
But I'd guess at Toppys.

[Howie]

ok i hope somene can help here.At one time I bought a R100 gs and was looking at an old Topo map,for roads routes .Then i had an idea to place the NI tag o rama at an intersection using map references.I thought map references were literal long lats but maybe not?I also found that NZ has a new mapping/survey? system which further confuses me.
So the question to the gurus is,if i place a map reference from a 1996 1:50,000 Topo map is this something that can be used by an owner of a newer series topomap or a gps? For example a certain establishment has a topo map reference of r28,r27&ptQ27 893770,and i will meet you there for lunch.Where am i going to meet you?

The map reference you are talking about at a guess is on a R serries map 28, and 27 not sure what you are refering to with Q27. R27 is the Wellington map, but I can't find my copy to tell you where :no: Map reference's are only applicable to the same Map serries as you are working from. The edition of the map doesn't matter, although later versions well have more upto date information on them. Where as GPS co cordinates of "degrees,min, seconds" are universal. if you look closely at your topo map it should show degrees and min on it, but well only cover about 1 1/2 min depending on scale.
I know you can enter "degrees, min, sec" coordinates in google maps and come up with a location as I have used that before, not sure if you can get that info from google maps though. Maybe google earth would do that for you?

[BMWST?]

The map reference you are talking about at a guess is on a R serries map 28, and 27 not sure what you are refering to with Q27. R27 is the Wellington map, but I can't find my copy to tell you where :no: Map reference's are only applicable to the same Map serries as you are working from. The edition of the map doesn't matter, although later versions well have more upto date information on them. Where as GPS co cordinates of "degrees,min, seconds" are universal. if you look closely at your topo map it should show degrees and min on it, but well only cover about 1 1/2 min depending on scale.
I know you can enter "degrees, min, sec" coordinates in google maps and come up with a location as I have used that before, not sure if you can get that info from google maps though. Maybe google earth would do that for you?

Its a 260 series topomap of "Wellington"

R27 is the wellington map,R28 is a bit tacked on the south,and Q27 is a bit tacked on the west side ,otherwise they would have 2 maps of mostly sea with a little bit of land at the top or side

[BMWST?]

You may not turn up though.


But I'd guess at Toppys.

Correct
Nope,Martinborough doesnt appear on this map

[warewolf]

"R27" is the sheet, and the 6-digit grid number on that sheet (makes sense to me). The sheet is required for uniqueness nationally, but usually dropped once the local area is defined. This is called colloquially "NZ Grid". In days past, is was very useful to have a GPS with NZ grid on it, as well as lat/long. Historically most field references were NZ Grid, so it was useful to have a GPS that didn't require you to convert to lat/long first.

NZ Grid changed sometime in the sixties? seventies? as the older (imperial?) topomaps had the old grid numbers.

No doubt there are much better sources than me, heck I don't even own a GPS!! Bound to be discussion ad nauseum on advrider. Also check the NZ Land Sar website for tutorials or other info on how to use a map and quote grid refs.

And lat/long has 3 representations; degrees, minutes, seconds; degrees, minutes with decimal fraction for seconds; and degrees with decimal fraction for minutes and seconds. Just the other night I had to futz around for a while converting between those three... gaahh!

[Cloggy]

For example a certain establishment has a topo map reference of r28,r27&ptQ27 893770,and i will meet you there for lunch.Where am i going to meet you? You'd be meeting me at 644mtrs above sealevel on a point of the Whakanui Track in Wainuiomata. Or thereabouts as giving your location in those co-ordinates is only accurate to about 100mtrs. The co-ordinates on our GPS would be showing around 41°17'09.3S and 174°59'38.4E
You can convert the old NZMS 260 Topo map co-ordinates on this LINZ site:
http://www.linz.govt.nz/geodetic/conversion-coordinates/online-conversion-service/index.aspx
The co-ordinates on map R27 893770 are actually 5989300 and 2677000 (as shown in the bottom corners of the paper map) and are the NZMG (Mapping Grid) which has been replaced by NZTM2000 (Transverse Mercator). There are links at the bottom of the LINZ page given above which explain the differences between these standards and why.
Most Garmin GPS units can display co-ordinates in NZTM but not the NZMG.

[koba]

ok i hope somene can help here.At one time I bought a R100 gs and was looking at an old Topo map,for roads routes .Then i had an idea to place the NI tag o rama at an intersection using map references.I thought map references were literal long lats but maybe not?I also found that NZ has a new mapping/survey? system which further confuses me.
So the question to the gurus is,if i place a map reference from a 1996 1:50,000 Topo map is this something that can be used by an owner of a newer series topomap or a gps? For example a certain establishment has a topo map reference of r28,r27&ptQ27 893770,and i will meet you there for lunch.Where am i going to meet you?

The topo map you are reading of is an NZSMS 260, the current sandard for 1:50,000 in NZ.

To answer the easy bit, the owner of a newer series topo map will be able to read it directly because the ones you can buy right now are the same bar the usual ongoing revision.

The flash new TOPO50 maps aren't released yet, they are due out in september.

The grid on your topo you have there is not Long/lat, but some of them have a basic long/lat scale in black around the border, it is not very fine though and is just for a basic reference.

The grid on your topomap is "New Zealand Map Grid" or NZMG.

Long/Lat is not consistent either and it depends on the projection used so care must be taken not to get totally confused!

Most GPS systems and the NZSMS 260 topo maps currently use WGS84 projection. (Not on the map grid though!)

Is is a bit of a task to manually convert co-ordaintes between this and somthing you can use on a GPS directly, luckily you don't have to because LINZ have a handy calculator here (http://www.linz.govt.nz/geodetic/conversion-coordinates/online-conversion-service/index.aspx) this can be used to unter the FULL NZMG co-ordainates and convert them to WGS84, appropriate for most GPS users.

I don't have a Topo on me but look closer again at the grid and you will see at each end there are a bit more to the co-ordainates, there are numbers in the corners that you need to tack on to the front of your co-ordainates to give a total of a 7 digit Northing (the across lines) and 7 digit easting (Up/down lines).

This will soon be superceeded by NZTM2000 but thats somthing to worry about later but if you wan't to read about how they affect GPS users look here. (http://www.linz.govt.nz/topography/projects-programmes/topo50-project/gps/index.aspx)

This LINZ (Land Information New Zealand) Websize at www.linz.govt.nz should have all the info you ever need and more, if it doesn't e-mail or ring them and they should be able to help you out.

[koba]

You'd be meeting me at 644mtrs above sealevel on a point of the Whakanui Track in Wainuiomata. Or thereabouts as giving your location in those co-ordinates is only accurate to about 100mtrs. The co-ordinates on our GPS would be showing around 41°17'09.3S and 174°59'38.4E
You can convert the old NZMS 260 Topo map co-ordinates on this LINZ site:
http://www.linz.govt.nz/geodetic/conversion-coordinates/online-conversion-service/index.aspx
The co-ordinates on map R27 893770 are actually 5989300 and 2677000 (as shown in the bottom corners of the paper map) and are the NZMG (Mapping Grid) which has been replaced by NZTM2000 (Transverse Mercator). There are links at the bottom of the LINZ page given above which explain the differences between these standards and why.
Most Garmin GPS units can display co-ordinates in NZTM but not the NZMG.

Haha, Beat me to it!

[BMWST?]

actually the co ordinates should be the lake ferry pub!

[Cloggy]

Interesting...
Have you got a map which shows all three parts at once R28, R27 and PtQ27?
I have seen the combined R27/PtQ27 but not one which also had the R28 bit attached.
Highlights one of the shortfalls of using this coordinate system, how easy it is to make a mistake, and probably one of the reasons for changing it. I was looking on a paper map of just area R27.

[BMWST?]

Interesting...
Have you got a map which shows all three parts at once R28, R27 and PtQ27?
I have seen the combined R27/PtQ27 but not one which also had the R28 bit attached.
Highlights one of the shortfalls of using this coordinate system, how easy it is to make a mistake, and probably one of the reasons for changing it. I was looking on a paper map of just area R27.

yep,pic attached,and as it happens the lake ferry pub is also visible!
I would have though the co ordinates would not be visisble on just an r27 as they are actually in r28
I guess thats why they say to make the sheet nos part of the co ordinate

<a href="http://www.flickr.com/photos/30057073@N08/3577604095/" title="topo 001 by kiwiproflexrider, on Flickr"><img src="http://farm4.static.flickr.com/3336/3577604095_5fcabe2e73.jpg" width="364" height="500" alt="topo 001" /></a>

[warewolf]

I would have though the co ordinates would not be visisble on just an r27 as they are actually in r28
I guess thats why they say to make the sheet nos part of the co ordinateNo, the numbers on adjacent sheets should be unique, and contiguous. Quote an R28 gridref as R27, and you will notice the grid is off the R27 sheet, but you won't mistakenly identify the wrong location.

Move a number of sheets away, and they'll repeat, so you can find a different spot matching those numbers.