Very confusing photogrammetry: pixel, scale and accuracy

Question

As we talk about the specifications of Aerial photo then we need to assign the following:

- Cell size or pixel (for example: 10cmx10cm)
- Scale (for example 1:1000)
- Accuracy (error)

But I couldn???t know whether these specifications are linked to one another! 
Is there an empirical equation that calculates these specifications?

If we get an aerial photo, then we can know the cell size only, but what???s about the scale and the accuracy?

Thank you in advance,

Regards

Jamal

JamalNUMAN · Answer

The cell size and scale of the aerial photography should be available when the imagery is purchased.  I am not sure what you mean by accuracy.   For aerial photography there may be a tag on it, that will indicate all of this information. If the information has been removed, then you will have to hope the metadata will include the focal length of the camera or scale.  Trying to reverse engineer the information without the components may be very challenging.

There are resources on the web that discuss the photogrammetric calculations.

Accuracy is usually the result of a classification, which is obtained through an accuracy assessment.

Thank you Jeff for the answer.

I'm not sure why the properties of the aerial photos just shows the cell size but neither the scale nor the accuracy!

i didn't mean by the accuracy the one that is calculated from the classification! what i mean is the degree by which the digitized object are close to the actual value. for example, suppose that an edge of building is digitized to have 20 meter while the actual value of this edge is 21 meter, then there is an error of 1 meter between the digitized value (which is obtained from the aerial photo) and the true value measured on the ground.

likewise, if the aerial photo measures the elevation, then there is an accuracy in measuring the elevations!

how these values are represented on the properties of the aerial photo?

regards

Jamal

JeffreySwain · Answer

The cell size and scale of the aerial photography should be available when the imagery is purchased.  I am not sure what you mean by accuracy.   For aerial photography there may be a tag on it, that will indicate all of this information. If the information has been removed, then you will have to hope the metadata will include the focal length of the camera or scale.  Trying to reverse engineer the information without the components may be very challenging.

There are resources on the web that discuss the photogrammetric calculations.

Accuracy is usually the result of a classification, which is obtained through an accuracy assessment.