[Tagging] [sharedmapau] Mapping surveyed marks

[Andrew Harvey]

On Wed, Jul 20, 2011 at 7:50 PM, Elizabeth Dodd <edodd at billiau.net> wrote:
>  Firstly, the mark shown in the nearmap imagery posted is a photo
> control point, for aerial photography. They are not a great deal of
> use because they are placed by private companies and are typically
> only in place for the few weeks that the survey is taking place. Areas
> such as mine sites may have more permanent ones, but they are still
> privately owned. There are no publically accessible location data for
> such points.


>        As for the survey marks in general, I think that adding them to
> the map is a good idea. However, it is important to remember that
> surveying is a state controlled industry. Each state would have it's
> own rules for the placement, naming and numbering of marks. I worked
> across 2 states in the survey industry and the marks can be
> surprisingly different.

Numbering can be managed via the ref tag, postfixed with something
like :nswssm to indicate that this reference id is for SCIMS State
Survey Mark number.

e.g. ref:nswssm=35225

>        SCIMS lists 7 names for types of survey points. Of them, I
> think that only the Mapping Control Point, Cadastral Reference Mark,
> and Trigonometric Station are worth including.

I saw those 7 SCIMS names from
http://www.lpma.nsw.gov.au/survey_and_maps/scims_online/glossary

They seem universal and easily applicable to other states and other
countries. So for now I'm using this same terminology for my tagging.

>        Any marks on the ground for positioning aerial photography (or
> other remote sensing) would be a Mapping Control Point. They will
> probably not be permanent.
>
>        Any small but permanent mark in the ground would be a Cadastral
> Reference Mark. The Cadastre is the register of land boundaries and
> ownership, and it is defined in Australia by distances and directions
> from several Cadastral Reference Marks. State Survey Marks, Permanent
> Marks, and Miscellanous Survey Marks are all types of Cadastral
> Reference Marks.

Interesting. Two features I've encountered which would fall under this
category, but I thing should be tagged differently are white pegs, and
small metal disks with a nail or something in the centre which have
"STATE SURVEY MARK" engraved... How would these two fall into SCIMS?
They may both be CR's, but I think they need different tags as they
are different. I would have thought the peg would be a CR and the nail
an SS since the nail says "STATE SURVEY MARK"...

>        Trigonometric Stations are generally older then Cadastral
> Reference Marks, and are known more accurately. These are generally the
> stations on top of hills with the black 3 or 4 legged stand, 4 metres
> tall with a top section made of 2 perpindicular circles. Back before
> satellite positioning, even back before electronic distance
> measurement, those stations were put in place and located simply by
> measuring the bearings to them, from any other station that could see
> them. Then the whole network across a state was adjusted to minimise
> the errors in the angles.

Yep.

>        I would not worry at all about the Geodetic Bench Mark type.
> There are few of those in Australia, and they refer to devices like
> tide gagues or permanently operating GPS receivers that are used for
> country or planet wide position determination.
>
>        I hope that I have made things clearer. If not, I am available
> to answer further questions.
>