A camera has two or more color elements that are removable and replaceable. The color elements may include a lens, a color filter with a filter data interface, and an image sensor. A security processor includes a private key, firmware, and has storage room for one or more vegetation indices. The security processor securely decrypts, stores, and uses the indices. Firmware checks license terms and installed filters required in a selected index, and analyzes images based on a formula in the index, thresholds for the index value, and thresholds for an object's height above ground level. A positioning receiver (e.g. GPS) determines time and position, which the firmware uses for the license check and for the height AGL calculation. Differences in camera position allow determining a parallax calculation on correlated groups of pixels. The camera provides on-the-fly analysis, and tags and stores images for which alert conditions are met.