Considerations when plotting old location data

[eruptn 95]

Question for the navigators and cartographers.

 

I’m working with some very old mapping data of the hot spring areas … in one report I have a couple of latitudes and longitudes. I’m wondering what considerations I need to give in plotting them to a map to day. The data was collected in the 1860’s and I assume as a sun shot or similar.

 

 

Thanks

 

 

[Fish 0]

I'm no expert, but the chart coordinate system would be a major consideration.

The most common for charts and GPS's these days is WGS 84 (World Geodetic System 1984).

I'd have no idea what 1860's data would have used.

 

The most common reason for survey stuff ups (at least in Civil design work) is the wrong datum. This was a barrel of laughs in Chch after the quake, when the land was out of whack with the previous datum (or survey base points) so they introduced a new datum. Old data was typically on the old (wrong) datum...

 

How critical is the application? are you trying to find a historical spot for some volcanolgy work?

[eruptn 95]

Yes .... trying to locate where an old map was made. Yes I'm well familiar with ground deformation; click on any blue triangle here: https://www.geonet.org.nz/data/gnss/map

The plot is mm of displacement since the site was built ... note they only show the last 7 years by default.

 

I'm assuming I can put the coordinates into a grid transformation formula and it will pop out the coordinates I can plot on a modern map .... just want to be aware of the fishhooks.  I'd be happy to know I was within 5-10 m.

[Fish 0]

Well I'm not a surveyor so don't know the finer points of it, but if you are just trying to find the approximate location I'd just whack the historical points onto a modern map / GPS and hope for the best. I think it's safe to say that any data points from 1860 will have its own unique set of inherent errors anyway, and the difference in modern datums is probably within that margin of error anyway.

[grant 40]

Have a look at the LINZ website, they have an on-line converter and more datums than any normal person would know what to do with. At the same time talk to them as they might be able to make intelligent guess about which one you should use

[idlerboat 116]

You may find the free program   SAS planet helpful. 

It is quite user friendly for geo type stuff.. (and dont be put off by the fact it is Russian) 

It allows you to put multiple mapping overlays in place and switch between them.

(Including various Sat earth sets)