Geog for 1/3, 1C: Reading Topographical Maps (Grids)

Hello 1/3 and 1C!


As promised, here's my post on how to read topographical maps. I hope it will help you understand the topic better. Allow me to nag again...this chapter is incredibly important because it is going to be a large part of your common test 2. This + longitude, latitude. *winks!*

If you recall, topographical maps refer to maps that display both physical and human features. But what does physical and human features mean?
Physical features = natural features like mountains, hills, rivers, lakes, ridges, valleys -> any feature that is NOT manmade. Human features = manmade features like schools, houses, jetties, reservoirs, plantations -> any feature that IS manmade!

To read topographical maps, we need to know how to read GRIDS, BEARINGS, DISTANCES and CONTOURS. This post will focus on grids, otherwise it will be a super long post!


1) GRIDS

First of all, a grid looks like this:



A grid divides a map into different sections that can be indicated by grid references. A grid is made up of eastings and northings, much like longitude and latitudes. Important to note: eastings are vertical lines (lines 16, 17, ..., 21) while northings are horizontal lines (42, 43, ...., 47). Don't get confused! There are 4 digit grid references and 6 digit references.


4 Digit Grid Reference


Let us look at 4 digit grid reference first. The 4 digit grid reference would be a number like that 1945. Hm! What does that mean!


A 4 digit grid reference always always refers to an area, which means an entire square in the grid. Next, the grid reference is always arranged Easting - Northing. never never Northing - Easting. This means, in 1945, 19 = Easting and 45 = Northing.


But! the 4 digit grid reference gives us the intersection point of 2 lines, not an area! so which area is it! *confused yet?*

If we look at the picture above, 1945 is the intersection point of the lines in the middle of area 1, 2, 3 and 4. So does 1945 refer to 1, 2, 3 or 4!!! HELP!

Well, some of you have already heard this.
The Elephant's Nose always points to the Broken Large Coconut. it translates to
The Easting and Northing always points to the Bottom Left Corner of the square.


Thus, 1945 refers to area 2, since the point 1945 is the bottom left corner of square 2. Hope i have made it slightly clearer instead of confusing you!

That is all for 4 digit grid reference! Must must remember that it refers to an area!


6 Digit Grid Reference

4 digit is already so confusing! why add 2 more numbers! =(

Well, 6 digit is actually slightly easier than 4 digit i feel. While 4 digit refers to an area, 6 digits refers to an exact point!

If we zoom into square 1844 from the diagrams in the 4 digit part, we'll get something like the picture above. And if we split the square equally into 10 parts between 18 - 19 and 44 to 45, we will get the diagram above!


Understanding from the diagram above, point 185443 will refer to the red dot. 185 is the easting and 443 is the northing. We read it the same way we read the 4 digit reference! It looks like an area now but imagine if we shrunk it back to the big map, it will become a single point.


I know that the maps you are given are not split into 10 parts for you! So what do we do? Very simple! We take a ruler and measure for ourselves! Then we find the point of intersection between the easting and northing and we will get the point we need! YAY!


So what is the point of having 4 digit grid reference and 6 digit reference? Why can't we just use one of them?


The 4 digit grid reference refers to an area, which is useful when we want to talk about features that occupy a large area. For example, an island, a lake, a reservoir, a plantation, forest.


The 6 digit grid reference refers to a point, which will be useful when we want to talk about a feature that occupies a small area. For example, a school, a tree, a jetty, a shopping mall!


See? It's all very simple! and really useful in everyday life too! Especially when you're reading a street directory! I couldn't find any good online quizzes for this part. Sorry! I will quiz you when school reopens though! So make sure you all know these! =))


Next up will be bearing and distances! Hopefully by wednesday! Let me know if any of you have questions about your homework!