# Calculating the Distance between a Special Object and Center

I just want to detect a small object specified in the system and show the distance between it and the object. If I need to explain briefly; I want to detect a small object that I put on the foot of a bird when it approaches 10-15 meters to its cage and measure the distance between them. I plan to have a device that scans around, like a radar. When there is a special object approaching this tool 15 meters, I need to detect it and measure the distance between them. (for example, 12 meters now, and 9 meters after 3 seconds). I thought that if i use a very small (electromagnetic or infrared ray, etc.) signal emitted by the small object attached to the bird's foot, the continuously operating radar can detect this particular signal. Also, it should measure the distance between radar center and the signal. It's like a bluetooth device. But also, it should measure the distance between radar center and the signal. But I could not find a sensor to do this. (I tried to explain briefly in the photo)

Do you think which product should i use or what should i do for this? Thank you

• How big a bird are we talking? Anything "active" will need a battery, and that will need a golden eagle to carry it on its ankle. – Majenko Jul 12 at 15:12
• How long does it need to last? A super cap is light and might last for minutes to hours. But will eventually need an energy source. Also, you never required a heading - only distance. So any number of COTS technologies which indicate signal strength should work. – st2000 Jul 12 at 15:19
• Dear @Majenko , Thank you for your comment. Unfortunately it’s not a golden eagle :( . I understood what you mean. I’ve been searching this subject. And I learnt that there are products to find out where homing pigeons went to by saving coordinates for weeks. I think saving enough energy in a small battery can be possible to do this. I just want it to work 2 or 3 hours – user10533354 Jul 13 at 14:50
• Dear @st2000 , Thank you for your comment. I want it to work 2 or 3 hours. And you're right about energy source. Do you think which product is the best to measure the distance in this situation? If you don't mind, could you please give a product name ? – user10533354 Jul 13 at 16:10