Map indexing - number of points plus a few other GPS logging questions

I searched for an answer and it’s not clear. I am creating a GPS logging capability for a remote controlled vehicle. As long as I maintain WiFi connectivity I believe what I want to do should be possible. Besides location data, speed, time of day, etc… from the GPS I will be collecting engine RPM and temperature possibly with some other variables. Making sense of all of this data will be the difficult aspect of this project. I’d like to leverage the map interface if I can.

  1. Map the GPS data with a series of index data point. Is there a limit to the number of data points? If I collected position data at 1-10Hz will I have any problem flooding the server with data? Is there an index limit?

  2. Within the map function a “value” label is shown. I’d like to superimpose “Measured Speed” at that data point. I believe if the user selects that point on the map then the speed should show up if I format the value properly. eg. If 45.3MPH could show up for a selected index point.

  3. I’d like to have a switch to select “other values” that may have been collected at the same map index position. Perhaps engine RPM, or time of day can be selected and shown on the map. Is it possible to apply multiple data types to that single “value” in the map?

  4. I also plan to save locally within the ESP8266 values such as peak speeds, peak RPM, and possibly temperature. I’d love to be able to then identify where in the index (the map) those events occurred. Is this beyond the scope of that tool?

  5. Lastly I would like to be able to save a data set to a file or other storage medium for later retrieval or viewing. Other than some other link to another service does Blynk have that capability? Yes my hardware theoretically could index the various data sets and retrieve them for review but trying to understand what I can do on the server vs. on the hardware is the essential thing I’m trying to understand.

From my experience with Blynk and GPS I would say Blynk and an ESP8266 can handle most of what you require.


Been trying to convert my speed data (float) to string data so I can experiment with the label in the map. I would like that label to be my V3 data (floating point - spd). I tried directly using V3 and the nuber 3 is all that shows up on the map when the icon is selected. Not having any luck. I thought I saw an example of this earlier but can not find it for the life of me.

Have you checked i in the app for the widget?

Yes - looked through the help and in the app for the “value” string. I only see typical uses where a label is printed. I would like for that label to be my data at that index. Believe I just need to convert the spd data from float to string. Sorry not a programmer but a hardware guy so this is likely easy but I’m struggling!

Ah I thought you knew how to do float to string.

If ever you are struggling just get Google to give you the answer.

From a search like “C++ float to string” gives:

OK Now I feel stupid. spd (my Speed for the GPS parser) was entered as a float. Never dawned on me to try to define it as String data! I tried this and it worked:

myMap.location(move_index, latitude, longitude, String(spd,2));

Next is number of index points for the GPS data? Is there a practical limit? Server limit? I can easily 10,000 to 100K points for a successful logging event. When i want to display an alternative string for the GPS points I think I need to just rewrite the entire index over with the prior GPS location data but the new string value. I’ll have to store all that data locally in the ESP but that should be possible.

Do you know if the GPS points can be highlighted? If I have 10K points on the map and only two of them are important I’d like to highlight where on the map the pertinent data occurred. For example for maximum speed it would be nice to find out where on the map that took place. Of course I will know which one from the 10K data points but how can I make that stand out vs. all the other black points on the map? Ideally the ability to color code the map data points would be perfect. Perhaps that could be an enhancement if not already available. I guess I could clear the map and only show that one data point but that seems a bit severe.

When I took my Blynk server (Rpi Zero W) and GPS with ESP8266 on a test drive it recorded for hours without a problem but I can’t remember what the refresh rate was.

@Dmitriy is there a server limit for map datapoints?

Dunno about highlighting but some of Blynk’s other widgets like notify and email might come in handy for that.