Originally Posted by Trip in VA
It takes terrain fully into account. The model is the same model used by the FCC, the widely accepted Longley-Rice model. It, like anything else like this, is a projection. It makes assumptions of ground clutter, amount of signal that will diffract over terrain, etc. that sometimes work better or worse depending on the specific circumstance. Here's a great example that goes the other way:
At that location on the Interstate, barreling down the highway at 70MPH, I've decoded WVIR, WHTJ, WRLH, WTVR, WRIC, and WCVE more than once. While moving. On a Silver Sensor antenna inside the vehicle, with and without amplification. This is at mid-day, not during an atmospheric event. People in the valley regularly watch those stations, as in greater than 90% of the time. The model predicts significantly less signal will make it over the mountain than actually does. Yet if the model was corrected to account for that in this instance, you would see the predicted strengths on your example locations go up even more, because in your area the signal diffraction is not nearly as effective.
I have no disagreement with your general argument that it's a prediction and needs to be taken with a grain of salt. I understand that and agree with that. My only dispute was with your singular argument that the models do not take terrain into account, or to use your words, "their predictions are based strictly on data in an ideal world that's flat," which is demonstrably untrue.
I agree, the Longley-Rice model appears to take into account the terrain and/or clutter.
A little, tiny amount.
I can't speak for your location you mentioned, haven't really seen it.
If you have Google Earth, you can view my examples as they have the street view. Put in the example 2818 4th ave north, Seattle, WA, and when you get there, go to the street view. Spin around so you're looking south. That street is so steep, the car they used to take the pictures couldn't even level it out. Check the houses, trust me, they aren't all tilting and falling over! The street is one-way down only. You can loose traction in the rain trying to go up. The hill rises to the south over 200ft in a matter of 2 blocks and continues to 300ft above this in another few blocks. According to the TV Fool report, another slam dunk for KIRO, KING, KOMO, and KONG. You're only one mile from the towers, as the crow flies. However, reception is zero here. It's a relatives house. We tried everything, even thought about VooDoo. In the old analog days, she had a 30ft mast and got nothing but ghosts, but could hear some TV, so that's what she used until cable came in.
According to the report, those first 4 channels are LOS. Even taking that with a grain of salt, or even a mountain of salt, it shows that the terrain portion of the FCC's model is waaaaaaaay off. And in fact, none of those channels listed there can be had. To the southeast is a little thing called the Aurora Bridge, couple of tons plus of steel and concrete blocking signals from there. To the southwest, for KCPQ ch13 VHF, there's 400ft elevation of hill in the way, for over a mile.
In the 3163 SW 172nd st, Burien, WA report, it says that the stations in red may need a rooftop antenna. Okay, I'll give them that. Try 300ft up and then you will see those stations. The cliff behind these homes rises to 275ft above sea level in just one block as the crow flies. All the main Seattle channels are straight into that cliff and hill, except FOX KCPQ, which goes sideways across the hill, and is very hard to get with a big yagi, yet says LOS on the report.
These two examples are the worst cases, but it shows how very far off their terrain model is. AND, because of that, it really skews the results for predicting reception in our part of the planet, a lot. Granted, in some of the locations where the hills and other obstructions are not a factor, then it's working a bit better. Even then, though, it doesn't appear to take in to account the transmitting pattern differences, like I mentioned at the Duvall address.
Thanks for the info, Trip, learned a lot.
Which all brings me back to my original intent.
For people expecting the results of a TV Fool report to be the end-all be-all, don't. Take it for what it does right, number of possible stations, directions to them and distance in miles. As for your reception possibilities, it's not very accurate. Look around your site. If you're buried in the trees, down in a gully, more than 50 miles away or have a big hill close by and between you and Seattle, then you probably have some challenges. What are your neighbors using? If you see an antenna on a home nearby, stop and ask how many channels they are getting, how well, and what they are using.
That's going to be the best predictor for reception at your home.