Ep 8 & 11: Not explicitly stated which CHM file is used in either episode

[kristi-sara]

So. I asked earlier about the pull requests but I realize this is wording and I'm not sure how you'd like to explain this in the lesson. Episode 4 is the first time we are introduced to CHM and then we forget about it until episode 8.

In episode 4 when we first use it, we use a mathematical formula DSM - DTM = CHM, instead of calling the actual HARV_chmCrop.tiff into rstudio. We use the CHM again in a challenge in episode 8 canopy height model challenge, but assuming instructors/learners actually do it, it is not made explicit in the instructions that a new CHM is read into Rstudio. When we ran the code there is a visible difference between the raster math derived CHM and imported CHM in the HARV data folder.

Raster math derived CHM, there isn't the white spots:

new/imported CHM tiff, output is identical as lesson:

If this challenge isn't completed for time or difficulty, in episode 11, part of the exercise is dependent on the CHM (again) and has the same confusing issue for the crop extent exercise. There isn't any text stating to import or st_read(....HARV/CHM/...). It looks like the lesson is using a new HARV_chmCrop.tiff for the challenge and the episode exercise.

Raster Math derived CHM, more green:

New/imported CHM tiff, output is identical to lesson: