GEG1240 - Maps and geodata

Map projection coordinate system

 

Goals:

 

Data foundation

http://ngis2.statkart.no/norgesglasset/fmr/default.html

 

Method

In this task we are going to use digital maps from “Statens Kartverk” (Norwegian Map Agency) which are called “Norgesglasset” (The Norwegian Magnifying Glass).

 

Click on the flag “fastmerkeregister” (Registry of reference marks). You will see a split window. Click on the button “Forrige Utsnitt” (Last segment) to get to identical views of Norway. Both windows can be used to zoom in and out with, but the left window acts as a reference window, where you will see a rectangle of the segment you have zoomed into in the left window.

 

By clicking in the window and while holding the mouse button, you can drag and make a rectangle to zoom in closer. Use the right window to zoom into the region around Oslo.

 

When you have zoomed close enough, you will notice that the type of map changes. Obviously, there are different series of maps that has been scanned and used in the application.

You can view the coordinates above the map. Notice that the prefix changes when the map series changes.

 

Explore the map. If you double-click on the left mouse button, you will centre the map on this location. If you double-click on the right mouse button, you will zoom out five times. The “Standard Målestokk” (Standard Zoom) button will zoom in (or out) to a fixed resolution. To understand symbols in the map, the Legend for Norgesglasset can be helpful.

 

This web application is perhaps not the most sophisticated, and the interface is not very intuitive, as it was created many years ago. But it serves the purpose of demonstrating different coordinate systems, as it has a seamless integration of different map series. A newer version of Norgesglasset exists, as well as the similar applications, Finn.no and Gule Sider.

 

Coordinate systems

Get the overview of Norway by clicking “Hele Norge” (Whole of Norway). Try to find Oslo/Blindern with the mouse and note the north and east coordinates as well as the prefix for the coordinate system (ks).

 

Zoom towards Oslo/Blindern and note coordinates and system for each zoom. Make a table.

 

Tip: To aid in this task find blindern first in the right map. When you start zooming down in the left window, you will have a small box to aid you.

 

Tip: If you find it hard to find the university, find the end of the Oslo fjord. The there is a vertical line in the map to the right of a half island (Bygdøy). Where this line intersects a “whitish” area, you should find Blindern.

 

Eventually you will get down to the university. Try and find the geoscience building and find the southwest corner.

 

Compare with this map from Oslo municipality (pdf). Use the coordinate system on this map to find the coordinates of the same corner. For an added challenge, use a ruler to extrapolate accurate coordinates.

 

1. Put all the results in a table (e.g. Using Word), and use the prefixes to try and find the coordinate system. Put the result into the table.

 

2. Are there any similarities or differences between the different coordinates? Anything that can tell us which coordinate system we are operating in?

 

3. What is the difference between the coordinates in the Oslo municipality map and the coordinates of the highest zoom from Norgesglasset? Can this tell us anything about the coordinate system in Oslo?

 

4. Try making a list of which type of map series appear as you zoom in, and try and say something about the scale of the map. To measure the scale, put a ruler on the screen and measure a distance (e.g. 5cm) in north-south or east-west direction, and find how much the coordinate (given in meters change).

 

Tip: To find the scale you need to divide the distance on the map with the distance in the real world (remember to convert to similar units).

 

Transformation

Go to the banner “Transformasjon” (Transformation): Here you can convert coordinates between the different coordinate systems used in Norway. The Norwegian terms is “fra/til referansesystem” (From/To Coordinate system), “Nord” and “Øst” (North and East) and “Høyde” (Height). The three next fields are where results appear. (“Feilkode” means error, which implies an improper or out-of-bounds value).

 

Take the coordinates you found for the geoscience building in the greatest scale (a.k.a. the closest zoom) – this coordinate should be in NGO1948 Gauss-K. Akse 3 as implied by the ks prefix – and convert it into EU89-UTM Sone 32. This second coordinate system was indicated by the prefix 22; you should have seen this at smaller scale.

 

5. Write down the resulting coordinates. Then calculate the difference between the transformed coordinates and the coordinates you measured at the greatest scale of the EU89-UTM system.

 

6. Transform the same coordinates to ED50-UTM Sone 32. Now you have the coordinates for the same corner of the building in three different datum’s. How great is the difference between coordinates in ED50 and EUREF89 (EU89) for this point?

 

7. The two lowest choices in the menu are for transformation into geographical coordinates (longitude and latitude). Transform into both “ED50 Geografisk” and “EU89 Geografisk”.  Find the difference in seconds in both the northern and eastern directions.

 

Distance

Zoom towards Lillehammer Church and find the coordinates of the south-western corner. Find them first in NGO Akse 3, as with the geoscience building and then transform this value into EU89. At this point you should have to coordinates for both Oslo and Lillehammer in two coordinate systems.

 

Tip: To find Lillehammer church, look at the top part of Mjøsa, a big lake north of Oslo. And orange area there should be Lillehammer. In the N50 map series you will notice the church symbol in the centre of the city. Zoom in on this until you see “Lillehammer Kirke”.

 

8. Calculate distance between the two points in both coordinate systems and compare these two distances. If they differ, what could be the reason for that?

 

Tip: Examine the fraction UTM/NGO distance.

 

Tip: If you want illustrations, you can take a copy of the screen by pressing Print Screen. Now the screen is copied as an image into the clipboard. Use the Paint program in Windows (or an equivalent) and copy it in using the paste function. Resize and cut the image. Then you can import or copy it into Word. This can be a valuable exercise if you are unfamiliar with this practice, as it is used much in later reports.

 

Resources

Trond Eikens Map Compendium (pdf)

Coordinate Systems

Map Projections