Thanks to our active tectonic plates, the datums of both countries are becoming rather outdatumed. For example, Australia has had about 1.5m of land mass shift from its 1994 position relative to the earth’s surface.
NZ has implemented its new datum NZGD2000 and projection NZTM2000.
On 1 January 2017, Australia’s first step in a multi-year process is heralded by implementation of GDA2020. The second stage is in 2023.
In Switzerland we are changing too from CH1903 to LV1995. So the reference system in Switzerland we are using is more than 100 years old and it takes more than 20 years from the new measurement to changing to the new reference system. — from Gian-Reto at OCAD Inc.
The latest Australian official advice re the datum changes is on the ANZLIC Committee on Surveying and Mapping website for GDA2020
Also worth reading is this presentation from RMIT.
For New Zealand datum change see the NZ Land Information website for NZGD2000
OCAD Co-ordinate Systems
The OCAD co-ordinate system combines datum with the country map grid. e.g. GDA94 Zone 55.
OCAD Inc already has in place the new NZ co-ordinate system based on NZGD2000.
When the Australian parameters are available, they will do the same for GDA2020.
Transforming from Old to New
Very simple. Under the Map | Transform menu you select Change Co-ordinate System, then select the new co-ordinate system and it is done.
Geostationary satellite image source Wikipedia
Not entirely unrelated
GPS registers most accurate signal yet. NASA aerospace analysts recently calculated the signal-in-space accuracy of GPS to 38 centimeters. Good news for farmers and auto-drive car developers. Read more and also click the image at top of that reading for GPS info you might not be aware of.
The ELVIS output format Esri Ascii Grid, can be imported directly into OCAD 12 via the Import Wizard in the DEM menu. So you not only have an easy way of obtaining the data, you also have an easy way of using it. (See my earlier post ELVIS rocks with LiDAR contours on the basics of using ELVIS).
ELVIS LiDAR vs state geospatial vector contours
For a small area of Anglesea used in 2015 for a mountain bike orienteering event, I downloaded ELVIS LiDAR and VicMap vector contours. Then overlaid them in OCAD.
The brown contours are VicMap 10m obtained via download of vector form via Shape file. 25m index contours were also obtained but do not appear in this fragment.
The other 3 colours are from ELVIS LiDAR data;
grey is 1m (shown only in second image)
green is 5m
purple is 25m index contour
At first glance there is a general consistency if we ignore the many minor indentations in the LiDAR lines that could be easily smoothed in OCAD.
However the 1m LiDAR does indicate the existence of two lower parts of gullies that are shown in the VicMap contours, albeit the eastern displaced. So maybe 1m contours could usefully inform the mapper at draft stage in some map areas.
This is similar to the result when smoothing in OCAD except that Karttapullauten has interpolated 2.5m contours (the dashed lines). Interestingly, this makes the progression of the above mentioned eastern gully much easier to observe.
When you download ELVIS data, it is the .asc file that OCAD DEM import wants,not the Shape file.
If you get nothing showing after import, then check the .asc file content. You can use any text editor to read it. In the header lines there is a value for NODATA. If the file is composed completely of that value then there is no LiDAR data for the area you selected. ELVIS now warns you if there is no data in the selected area.
When you are asked which co-ordinate set you wish to use, unless you have set up your OCAD file to match the location of the imported DEM data, then select the upper set which is that of the DEM data. Else the DEM data will likely be located far beyond the reach of your OCAD map area.
If you expect to frequently use LiDAR data, then importing into a special OCAD file can be a boon, It should be empty and have just essential symbols that don’t clash with standard symbols for when you import that OCAD file into your working file. Such a template is downloadable from the section immediately above.
ELVIS is Geoscience Australia’s new elevation information system. It is free, licenced under Creative Commons and makes public LiDAR data very accessible. Thank you to Russell Rigby, mapping convenor ONSW who made me aware of ELVIS. The LiDAR data available is;
SRTM-derived 1 Second Digital Elevation Models Version 1.0
DEM SRTM 1 Second Hydrologically Enforced
5 metre Digital Elevation Model (DEM) – this delivers 1m, 5m, 25m contours
I downloaded 5m DEM data covering part of the 2015 Anglesea mtbo map, imported contours into OCAD and overlaid those on the OCAD map file of 5m contours. The correspondence was very close which is a tribute to mapper John Sutcliffe as much as to the ELVIS data.
The 5m resolution coverage, which provides down to 1m contours, is fairly thin. These surveys cover Australia’s populated coastal zone; floodplain surveys within the Murray Darling Basin, and some parts of major and minor population centres.
Maybe we will see more sand dune coastal area maps akin to those near Hobart, Auckland, Levin and Invercargill. And perhaps street and park-O where more detailed contours are desired.
Ease of use
The website isn’t yet the friendliest until you get to know it and then it does work well. Here are tips based on my learning;
Symbols of available datasets
Selecting a right arrowhead symbol provides a synopsis of that data type.
Selecting a download arrow symbol takes you to the selection of data coverage for your project.
Selecting the globe symbol, (red when selected) shows on the map at left, the available coverage for that data.
Selecting the ‘eye’ symbol (orange when selected) show the extent of that data coverage.
Note the latter two symbols act like check boxes, not radio buttons.
Selecting a 5m dataset
At time of writing, selecting the name of any state 5m dataset gives you identical national information. It also has links at right (when selected) to state mosaic downloads – these are of no relevance to OCAD use.
Selecting the download icon frames the 5 metre DEM coverage area for that state.
Download of data
Whichever dataset you choose, the method of selecting data is the same. The download wizard is easy to follow.
For Output Format, select Esri ASCII Grid for OCAD import. The file will be a .asc type file.
For Coordinate system, select GDA94 for OCAD import.
Curious about spatial computing? Or more than curious?
This course from the University of Minnesota via Courseradelves into spatial computing for geographic information systems (GIS). Now that might seem heavy going but the course caters for three different goals of participants;
Curiosity – learn about one or two spatial concepts of interest to you
Concepts – learn about spatial concepts but not get involved in programming or statistics
Technical – the lot!
Why might this course interest you?
If, like me, you use data from various sources then you will doubtless have run into issues ranging from data formats to co-ordinate systems to projections to …. So you might want more than a passing knowledge of what you are dealing with.
I am hopeful the Curiosity track will increase my knowledge of co-ordinate systems and projections so I can bother Russell Rigby a little less. And if I can get through at least some of the Concepts track maybe I will further broaden my knowledge of ESRI Shape files and the like as I use them in nearly every map I produce.
This course introduces concepts, algorithms, programming, theory and design of spatial computing technologies such as global positioning systems (GPS), Google Maps, location-based services and geographic information systems. Learn how to collect, analyze, and visualize your own spatial datasets while avoiding common pitfalls and building better location-aware technologies.
Best of all…
It is free unless you specifically want a certificate of attainment.
You will find out that egocentric maps exist but they are not necessarily your maps 🙂 And did you know orienteering maps are allocentric?
Sign up here. But be warned, it does take a fair bit of time and commitment. 8 weeks of 4-10 hours per week. However I understand you have until Christmas to complete it.