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Question:Best Method(s) of Datalogging Location in the Field Without Cell Reception?

sarasage is asking a question about general: Follow this topic

by sarasage | May 11, 2021 20:16 | #26556


Problem:

We are testing air quality with handheld devices that have internal dataloggers, but do do not have GPS. The area we are testing does not have cellphone reception and cannot rely on our phones to send data. Our project goal is to create a map with the AQ data results.[notes:air quality]

How can we design an automated GPS logger so that we can correlate the data from our handheld devices with a specific location?



9 Comments

@sarasage To make sure I am understanding your current configuration - You have handheld air quality monitors that log the results on the data logger, do not have do not have GPS, and currently rely on a separate application the needs an active cellular connection for entering the data.

A couple clarifying questions: * Do the data loggers have a way to connect to another device? - i.e. Bluetooth, USB, etc. * How are results currently logged and accessed? (Are they being stored to a file and transferred to another device? Are you manually entering the air quality results into another application?)

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Just going down that road a little bit further. What distance do you need to cover and at what data rate? There are wireless bands on 900mhz ISM ( industrial, scientific, medical) as well as FRS, MURs, GMRS bands. Some, like GMRS, need a license, although it's minimal. Others are license free but have to accept any interference. And don't forget the old CB frequencies and the 49 mhz walky talky freqs. I don't hear much on 49 mhz any more, if you need relatively short range and low data rates.

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@seankmcginnis @Ag8n I spent some time combing through the instrument manuals just now to answer your questions. Besides setting the instruments in their calibration stations (which double as data transfer centers), the only way to transmit data from the instruments is via an old-fashioned IrDA device.

The instruments can transmit data via: IrDA and via the proprietary calibration station. The manufacturer of the devices has their own software and exports AQ data to an excel sheet.

To clarify my original question, I think I am looking for a GPS device that can record multiple locations with a time stamp to be retrieved later. (Our monitors are set to record pollutant levels every 10 seconds). After a week of data collection, we can correlate the data from the GPS devices with the readouts from the air monitors, provided the times are synced. I believe some older geo-caching GPS devices do this. Most of the Garmin devices have color displays and stored maps, which is far more than what we need. We are familiar with the terrain and location, we just need exact GPS locations so that we can map ambient AQ levels.

Simply put, we need to know when and where the handheld devices recorded an AQ reading and we cannot rely on our cellphone's GPS because we do not get cell reception in the field. Does that make sense?

One quick edit: we are currently using an iPhone app, GPS Kit to get our coordinates when we are offline. It is clunky and I am looking to find a simpler solution.

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Yes,I see what you mean. Got a weird approach for the problem. First, please become a little familiar with rtlsdr dongles by going to rtl-sdr.com. The dongles cost about $25 and the article isbfrom tech minds ( Sept 1,2020). It talked about using an rtlsdr and an gps patch to decide gps signals. It would also take a computer. But... Might be a start.

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Thank you @sarasage - that helps. The AQ data is being captured in your data logger disconnected from the GPS coordinates being captured in GPSKit.

Your desired future state would be to have a single device that could capture the air quality information tied to the sample location feeding up to a datastore, whether the collector is connected or disconnected to a digital network (as @Ag8n referenced, we are lucky to have a lot we can pick from).

I hate to answer your question by asking more questions, but:

  • the cellular devices currently being used, are they iOS, Android, Linux, or a mixed bag of nuts depending on the person in the community?

  • do you or your organization have development skills or experience in building hardware or extending edge devices like a Grove, Raspberry Pi, or something similar?

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@seankmcginnis Yes, you are correct that our ideal future state would be a single device.

To answer your questions, we are using iOS devices and we are lacking in organizational hardware skills. Between members of my household, we can put together easy to intermediate Arduino projects. I would have to recruit an unknown someone in the community who has these types of skills to do anything more advanced.

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Hi Sara,

Just about any handheld GPS device (e.g., Garmin) or any GPS app for a phone (I use GeoTracker) will record a track. The GPS coordinates and time stamp are recorded every interval (user selected). No cellular or WiFi connection is needed to record such a GPS track (only GPS reception which is everywhere). The resulting data file can be opened in Excel, Google Earth, etc. Transferring the GPS data to your separate air quality data file will require some data management skill (the time stamps will not be identical, so some programming or manual manipulation might be needed).

You can find other devices that will record a GPS track (a file of time stamps and GPS coordinates). I built one to attach to my kite photography rigs (https://publiclab.org/wiki/skypod-gps-logger).

It is straightforward to add a GPS module to any Arduino data logger so the GPS coordinates will be recorded every time the sensor data are saved. But I assume your air quality data logger is not an Arduino device. So it might not be straightforward to add a GPS module to it. It is possible that your air quality device could send its data to an Arduino device (which could have a GPS module), but that might be tricky with a proprietary device.

It sounds like a simple solution is to record a GPS track on your phone while you are recording air quality data with the device. Then get both data files into Excel and figure out how to match up the time stamps (messy, but doable).

Chris

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@cfastie, Thank you so much for this helpful response.

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I want to update this post to say that since I posted this question, Esri has developed an all-in-one app called, ArcGIS Field Map.

It seems to be robust and fits our criteria. I shied away from using ArcGIS because it was prohibitively costly 10-15 years ago. Now, a subscription costs $100/year for individual use and the interface is much more user-friendly.

Shout out to @seankmcginnis for sharing his vast knowledge of Esri and mapping applications.

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