There are distance measuring apps out there, but measuring the diameter of a pipe presents a unique measuring situation.
Calibration. There will need to be some way of checking to see if the app is working correctly. You will need to measure a known standard to see if the app is measuring right. If not, there needs to be some way of calibrating or adjusting the reading, to make it accurate. In other words, if you measure a 2 inch pipe, and the app says 2.1 inches, you need a way to adjust the setting to read 2.0 inches. Otherwise, when you measure a 3 inch pipe or any size pipe, the measurement would be off.
Calibration should be done with different sizes of pipe, to make sure you will get an accurate reading at any of those sizes.
The curvature of the pipe needs to be considered. You aren’t taking a picture of a 2D object. The pipe is 3D, so your camera may not see the top and bottom of the pipe as being 180 degrees away from each other. If you are too close to the pipe, you wouldn’t see the full 180 degrees. So your measurement would be too small.
Resolution of measuring. A pipe diameter tape measure normally has a resolution of 100th of an inch diameter. Can a smart phone app be that accurate?
The nearness of the object. For calibration, we would need some standard distance from the cell phone. Maybe this could be accomplished by using an object like a 12″ ruler, placed between the pipe and the phone. Hopefully, a less mechanical method will pop up.
If you know of an app that can accurately measure pipe diameter, please let me know. If one does not exist, I’m sure it will be invented in the near future.
Lufkin® has a world-wide reputation for making high quality tape measures. They used to make them in the USA, but they have shifted the production facilities to Mexico. Some of the tapes are made out of a cast case, which is highly polished and chrome plated, like the w906pd. Others, like the w606pd have a stamped case, which is shiny and chrome plated. A third type of case is black plastic, like the asw616pd. However, the tape blade inside is the same in all 3 types of cases. It is capable of measuring diameters up to 23 inches.
Pi-Cobra is a brand name for diameter tapes made with
a cast case which is chrome plated. It can hold a longer tape blade, capable of measuring diameters up to 38 inches. The case is very durable. These are manufactured in China.
Various other Chinese manufacturers make versatile OD tapes like the 416-04-024-P. The back side of the tape measures diameter up to 24″ in 100ths of an inch or 610 mm. The case is plastic, and has a key ring attached to it.
The UT-56675 is made in the USA. It is capable of
measuring pipes up to 45 inches in diameter. This is a belt tape, not a pocket tape. The calibrations are in tenths of an inch diameter.
The popular Barlow Chrome Tape Measure number 20217. Why this product? The Barlow tape is a household word in many USA homes. The Barlow brand has a proud history of quality. Simplicity in design makes for a long lasting product life. The dual scale, metric and inch, make it popular in any country. The smooth compact design makes it a great tape to keep in your pocket. Your company logo can easily be laser engraved on the front and back.
Lufkin is a name you can trust. They know how to make an accurate pocket tape measure. An when it comes down to a detail, like putting a wider space between the zero mark and the next mark, they do it right. That extra space accounts for the thickness of the tape. The resolution is 100th of an inch diameter. It comes in a durable chrome-plated metal case. A company logo is imprinted on the front, and protected by a clear overlay. This is the best choice for a pipe diameter tape measure.
Diameter tape measures are able to give you the diameter of a pipe, pipeline, log, or any other round object. They do it in 1 easy step. All you do is wrap the pipe diameter measuring tape around the pipe and read off the diameter. A regular tape measure would give you the circumference. Then you would have to divide by pi (3.14159). That adds another step, plus you would need a calculator, pencil, and paper to arrive at the diameter.