If you use the feet to meters conversion of 1 foot = 0.305m instead of the 1 foot = 0.3048m conversion, will there be a significant difference in the elevation information, and therefore, in your analysis?
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Hello everyone, I have two DTM that I would like compare both of them. One of these has been considered as reference data. And this is my question.
Best answer by hkingsbury
The difference in your conversion values is 0.2mm or 0.00787 inches. Over the course of 1000ft, your looking at ~200mm difference (20cm, 0.2m) or 0.656ft.
On a flat plain, that difference is going to be inconsequential because you may only have 100s of ft of elevation change across many many miles.
In a steep area, where you may have 1000s of ft of elevation change across your area of interest, is your spatial resolution really going to be effected by 0.6ft of difference for every 1000ft?
I guess what i'm getting at is what is your use case for the data? this will decide whether you need the extra decimal point of accuracy.
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+63- Celebrity
- 1625 replies
- Best Answer
The difference in your conversion values is 0.2mm or 0.00787 inches. Over the course of 1000ft, your looking at ~200mm difference (20cm, 0.2m) or 0.656ft.
On a flat plain, that difference is going to be inconsequential because you may only have 100s of ft of elevation change across many many miles.
In a steep area, where you may have 1000s of ft of elevation change across your area of interest, is your spatial resolution really going to be effected by 0.6ft of difference for every 1000ft?
I guess what i'm getting at is what is your use case for the data? this will decide whether you need the extra decimal point of accuracy.
Thank you so much. This is just a question generally, for solving a student project. Then, as a result, it depends on it is better to be ignored, unless the project is sensitive and to be need significant accuracy. right?
+63- Celebrity
- 1625 replies
Thank you so much. This is just a question generally, for solving a student project. Then, as a result, it depends on it is better to be ignored, unless the project is sensitive and to be need significant accuracy. right?
The more accurate you can be, the better. Ultimately, your not going to be gaining much by using 0.3048 and you're not going to be loosing much by using 0.305.
If you were comparing 0.3 vs 0.3048 then there's a more significant difference.
It's a great example of diminishing returns.
But what would I do in the above? To answer, I'd want to know:
- What is the output of project, where is the converted data being used?
- What is the scope of the project?
- What is the accuracy, precision and resolution of the input data?
- What are the expectations for the client?
- How big is the area you're working across
Basically, its so dependent on the scenario. Where i'm from, we use the Metric system, and if i need to quickly convert between ft and m on the fly, I multiple/divide by 3, and that gets me close enough
The more accurate you can be, the better. Ultimately, your not going to be gaining much by using 0.3048 and you're not going to be loosing much by using 0.305.
If you were comparing 0.3 vs 0.3048 then there's a more significant difference.
It's a great example of diminishing returns.
But what would I do in the above? To answer, I'd want to know:
- What is the output of project, where is the converted data being used?
- What is the scope of the project?
- What is the accuracy, precision and resolution of the input data?
- What are the expectations for the client?
- How big is the area you're working across
Basically, its so dependent on the scenario. Where i'm from, we use the Metric system, and if i need to quickly convert between ft and m on the fly, I multiple/divide by 3, and that gets me close enough
This is not a big project, this is just a question generally. I have two Tiff file that one of them is considered as reference DTM and I have to compare both of them and have RMSE as a result. I attached the properties of them here. Both of them have only angular unit, different resolution . I don't know even how I can find the unit of them, whether Meter or Feet?!
