Welcome to UMSF, Dig.
> Tesheiner, the layer of your Route Map for Google Earth must be downloaded each time or if I keep the layer will be updated automatically?You should download it every time you see an update here.
> In Google Earth, the Mars view has a layer with the path of the Opportunity, which has differences with yours. Why are these differences?Good question. First of all, I presume you are talking about the different (x,y) positions for a given site in both paths. IMO the difference is probably due to a different translation from (x,y) coordinates to lat/long.
I'm keeping track of the route on a map-projected picture (HiRISE image PSP_009141_1780 in the route map you see here in JPG format) and the process to plot a position on that picture is in a way manual and results in (x,y) coordinates which are good for that image. Now, I'm creating the KML layer for GE automatically using a VB tool and converting the (x,y) into latitude / longitude using fairly simple interpolation. Besides, the HiRISE image you see in GE is not exactly the same I use in the route map. The end result is that these lat/long coordinates may have an error and/or they don't match the same point in both pictures, the one in my route map and the one used by GE.
In any case, this difference is only significant with big zoom factors.
Edit: Well, there are other differences too. One was noted by Doug and is because the path "embedded" in GE is updated only up to "Santorini". Another difference is that they are considering only the driving endpoints while my version sometimes use mid-drive points between two consecutive sites.