Spatial Resolution is described by the Ground Sample Distance (GSD), which is the distance on the ground between the centres of two adjacent pixels. The smaller the number, the finer the detail that you can see. Our equipment achieves 3cm/pixel.
Accuracy refers to the correctness of the location data (coordinates) within an orthophoto or similar product. Ultimately, this depends on the equipment making the measurements in the first place. Advanced survey equipment is used to record the positions of Ground Control Points in the survey area, and after the flight these recorded positions are manually correlated with the GCPs visible in the imagery. The survey equipment has accuracy specifications, and will also report its accuracy from moment to moment in real time.
There are numerous standards used to describe accuracy, but they all specify distance in one way or another. The smaller the distance, the greater the accuracy. A common standard is Circular Error Probability (CEP). This is defined as the radius of a circle, centered on the true value, which will contain 50% of the measurements. For example, our equipment will often display a CEP of 10 millimetres or better. This means that its claimed position can be expected to be within 10 millimetres of the true position 50% of the time. Perhaps a better, and more “demanding” standard is R95, which specifies 95%. In the above example, the distance becomes 21 millimetres.
By using accurate survey equipment and a good number of GCPs appropriate to the task, the accuracy of the final data should be high. This can be verified by placing around the survey area a number of targets whose actual positions are recorded, and compared to the locations claimed by the final orthophoto when you select those points in the image.