Shelley's Diaries for Geospatial
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Diary 3 - Wednesday 29 May 2013
Field Trip Name: Geospatial
Field Trip Place: Christchurch
Diary: 3 of 4
Weather: cold but sunny
Where's Shelley: Christchurch
Talofa lava, Shelley here.
The southerly storm brought snow to Christchurch overnight but fortunately the sun was out as we headed into the Land Information Office in the centre of Christchurch. The streets had a skiff of snow on them and the Port Hills looked stunning covered in a blanket of white. Our mission for the day was to learn more about topographic maps. We met Richard Freeman who is an expert in this area. Richard is a cartographer or map maker and he greeted us with an arm full of maps.
Making Maps
To understand how maps are made we need to think about what a map represents. Maps aren’t easy to make as they have to show the features of our round Earth on a flat piece of paper. This was hard to picture until Richard drew points on an orange and then carefully peeled it. The points he had drawn appeared further apart once the orange peel had been flattened out. Richard explained that some clever mathematics is needed to correct the distortion created when you map a round surface on paper. You can watch the video about this.
What’s on the Map
Richard works on topographic maps. These maps show the shape of the land and the natural and human-made features on it. We took a look at a Topo50 map and were surprised at just how much information it showed; everything from mountains, lakes, rivers and forests to roads, buildings and tracks. We could even see what type of vegetation was growing by looking at the different shades of green and the symbols in the map legend.
Quality Questions
Before leaving the warmth of the LINZ office we talked to Murchison Area School and New River Primary School during our audioconferences. Both schools had clearly spent a lot of time coming up with their questions. Richard talked about some of the cool technology that can be used to make map making easier and more accurate. GPS (Global Positioning Systems) have made it so much easier to know the location of something. GPS uses the time it takes for signals from four satellites to reach a receiver to calculate an exact location. You can listen to the recorded audioconferences to learn more.
Who Needs Maps?
It was fantastic to escape the city and head for the snowy hills. A surprising amount of snow had fallen around Dyers Pass and the views were amazing. You can see this in the panoramas. Richard broke out the maps again to explain exactly where we were. Alvin wanted to know why some maps show a lot of detail while others don’t. Maps are made to different scales so they can be used to cover larger areas in less detail, or small areas in more detail; like zooming into a picture. Lots of different people need maps to complete their work, or find their way in the outdoors. Emergency services rely on maps and Christchurch map sales increased after the earthquakes as people helping with the recovery needed to find their way around. The most commonly used map in New Zealand is the Topo50 map that has a scale of 1:50,000. This means 1 centimetre of the map represents 500 metres in reality. You can watch the video about map scale and just how far 50 metres is.
Which Way?
The sun disappeared behind high cloud and the temperature dropped so we headed back down the hill. Richard wanted to show us how to find out where you are on a map so we stopped by the Heathcote River and tried to find our exact location. We weren’t allowed to use our smart phones so had to apply some map reading skills. Before you can use a map you need to orientate it correctly so it matches the lie of the land otherwise you may end up thinking that something is in a different direction to what it really is – it would be like trying to read a book upside down! You can watch the video about map reading.
Map Apps
After looking at a paper map we wondered what a digital map looks like. We found lots of digital maps online and the great thing about these maps is that you can access them from your phone, iPad or tablet. There are lots of applications that help us in our everyday life and these all use geospatial data. You can map your training, find your way in a new city, find out about the tides or even find and name constellations. It’s hard to imagine life without this technology. But it’s also nice to know that when the battery on your phone runs out you can still find your way using a good old fashioned map!
See you tomorrow when we look at land elevation, nautical charts and how the earthquakes changed the seabed in Canterbury.
Manuia le aso
Shelley the LEARNZ Field Trip Teacher (and Alvin)
