Explain Georeferencing To Me as If I Were a Five-Year-Old

Blog post copied from Adrian Welsh on GeoNet 30/11/2016 – Too good not to share!!

Explain Georeferencing To Me as If I Were a Five-Year-Old

 

I really liked how Denzel Washington used the phrase “explain this to me as if I were a xxx-year-old” in the movie Philadelphia (1993).

Reference: Philadelphia. Philadelphia, PA: Jonathan Demme, 1993. film.

So, I will take it one step further and attempt to explain the concept of georeferencing to an actual five-year-old.

Five-year-old:

Five-year-old engineer says, “I have this PDF of a site plan. I want to put this on a map and have it line up properly.”

Here is my map.

We need to zoom in a little bit closer.

A little bit more.

Open Street Map 1:5,000

Almost there. Zoom in some more so that our site plan will fit better.

Open Street Map 1:1,050

Much better. Now, we need to shrink the site plan to a more usable size. Currently, it’s larger than our map.

Let’s make it a little bit smaller.

Perfect. Now we need to place the site plan on our zoomed in map and adjust it to fit by rotating it and resizing it.

Great! Now, after some quality control of adjustments and transformations, we can rectify this image and call it georeferenced!

OSM 1:1,050 with Image

We can make the georeferenced image transparent to where we can see the basemap behind it.

OSM 1:1,050 with Image, Transparency 50%

Finally, we can add existing linework and other GIS files to give the image a more solid reference.

OSM 1:1,050 with Image, Transparency 50% and Linework

Many thanks to Adrian Welsh for letting me share this!

Dragons8mycat