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LoRa | Geolocation

  • 4 november 2016
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Reputatie 7
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  • KPN Medewerker
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LoRa enables customers to use geolocation to track the position of your LoRa assets. KPN is one of the first providers to offer operational geolocation with LoRa.
This topic is about how to use geolocation with Thingpark and the LoRa Developer Portal.

Geolocation by multilateration

All LoRaWAN devices use broadcasting to send their messages. This means that all gateways within reach will receive the message and our core-servers will figure out what the message is and collect all received signals. One benefit of this approach is the ability to triangulate (or multilaterate) the location of the device when three or more gateways receive the broadcasted signal. Each gateway will receive the signal at a different point in time, depending on the distance between gateway and device. Note that the differences in time between gateways will be on the nanosecond scale, since the signal travels with the speed of light. From the time differences our core server can calculate the location of these gateways and forward the result to the application server. Note that no extra payload or signal needs to be broadcasted by the device. The beauty of geolocation in LoRaWAN is that there is no need for expensive chips or complicated payloads on the device side. The only thing needed is to instruct our Thingpark core to apply the triangulation calculation for a device.

Structure Geolocation in Thingpark

A connectivity plan can be configured for API messages to include geo-location information. Right now, this cannot be done automatically, but has to be done manually by our supplier. Selected customers can give us a limited number of DevEUIs which we will ask to be configured correctly.

When configured correctly, the usual API messages containing payload (DevEUI_uplink) will contain extra fields that say something about the location. An example can be found here. This will contain the following elements:

DevLocTime Timestamp of when the location was calculated. This can be significantly different from the timestamp of the payload
DevLAT Device Latitude in decimal degrees (see this wikipage for the different formats)
DevLON Device Longitude in decimal degrees
DevAlt This is not used yet, ignore for now
DevAcc This is not used yet, ignore for now
DevLocRadius This is not used yet, ignore for now
DevAltRadius This is not used yet, ignore for now

Asynchronous location messages

The API messages containing payload include the location as outlined above, but the timestamp of the location information can differ significantly, depending on the device uplink frequency. I.e. when sending once every half hour, the payload of the message will be forwarded directly, but location calculation can take some time and only be included in the next message 30 minutes later. To have access to location information as soon as possible a new type of message is introduced by Thingpark. This DevEUI_location only contains location information and is send separately. An example can be found here. It contains the same elements as outlined above. Note that the security token for this message is calculated in a different way, which will be added here later.

Provisions for geolocation testing

• The API message format will likely change in upcoming releases, so expect to change the parsing in your application server at a later time.
• KPN cannot guarantee availability or accuracy of the location functionality in this testing phase
• As always, devices have to obey the duty-cycle
• ADR is best kept on for static devices

There are two types of localisation messages, DevEUI_uplink and DevEUI_localisation. The first one is for the payload where the last known location is added to (independant of the time that has since past). Additionally, there is the DevEUI_localisation that is sent at the moment a location is being calculated. Below, you can find a link to examples of the JSON-bodies of both messages.

DevEUI_uplink
DevEUI_location

Where can I test Lora Geolocation?

KPN will offer nationwide outdoor LoRa Geolocation in the Netherlands. The Geolocation functionality is currently enabled on all gateways in the Netherlands (exceptions further down this guide). There are many locations and areas in the Netherlands at which the Geolocation function can be tested. The coverage and functioning of Lora Geolocation will keep improving while we make progress with the deployment of the network.

Accuracy of KPN Lora Geolocation

As tdoa (time difference of arrival) is the principle used for calculating the position of the LoRa device, environmental factors can cause reflections which impact the service. On average in the Netherlands in 90% of the uplinks a successful position is calculated. In 95% percent of those cases the accuracy is below 100 meters. Again, those results can only be expected for nonmoving objects.

Using LoRa Geolocation - Applications

Lora Geolocation can be used for all outdoor applications. In the current state it is important to know that the Geolocation improves as more messages are sent from the same location. Especially when you are using moving devices, we recommend that you take this into account.

Settings to optimize testing in Thingpark

For testing, we make use of a special connectivity plan that has been optimized for LORA Geolocation. This connectivity plan uses forced ADR and the antenna diversity setting is 3. In addition, we recommend to switch-on ADR for the devices that are used for Geolocation.

Geolocation in the LoRa Developer Portal

To enable developers to test their application using the KPN LoRa network and its geolocation functionality, the feature has been added to the Developer Portal. Users can choose to enable geolocation per device when adding a device.

By default you will receive the geolocation information in the DevEUI_uplink message you get from the developer portal as described under “Structure Geolocation in Thingpark”. Per device you can enable the asynchronous DevEUI_location messages as described under “Asynchronous location messages”. You can do this by choosing “yes” for “Enable GeoLocation” when editing your device:


Useful links

- LoRa: Starters Guide
- LoRa: Forum and Manuals
- LoRa: Dictionary & Definitions
- FAQ: Frequently Asked Questions
- Tools: www.LoRaTools.nl

59 reacties

Reputatie 6
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Hi @rharte,

Just to be sure I discussed your question about an empty data-payload with Geo-location with the specialists. The size of the payload has no influence on the calculation so it can be 0.

@Gabzz Thanks for clarifying your question. I understand what you mean now. I am going to discuss this with the specialists. When I got the answer, you are the first to know 😉
I expect to get an answer by Monday.
Reputatie 7
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Hi Jeroen,

The system isn't capable to calculate height coordinates yet. But it's a feature on the roadmap with no estimated time of arrival!
Hi Michiel

Yes, it makes total sense. The IOT device can remain simple and the servers do the number crunching..

Would the system also be able to calculate height coordinates?

Regards,

Jeroen
Hi,

Is my interpretation correct that I see contradiction statements in the opening post regarding ADR?
I read the following two statements:

1) This connectivity plan uses forced ADR and the antenna diversity setting is 3. In addition, we recommend to switch-on ADR for the devices that are used for Geolocation.
2) Please use SF12 with ADR off for these test. Note that in the final solution, ADR has to be switched on!

Is statement 1) about the default setting for the device once geolocalisation is fully available and statement 2) for the testing phase you're currently in? So, for testing geolocalisation now, should ADR be switched off?

Best regards,
Bert
Hi,

Is my interpretation correct that I see contradiction statements in the opening post regarding ADR?
I read the following two statements:

1) This connectivity plan uses forced ADR and the antenna diversity setting is 3. In addition, we recommend to switch-on ADR for the devices that are used for Geolocation.
2) Please use SF12 with ADR off for these test. Note that in the final solution, ADR has to be switched on!

Is statement 1) about the default setting for the device once geolocalisation is fully available and statement 2) for the testing phase you're currently in? So, for testing geolocalisation now, should ADR be switched off?

Best regards,
Bert


Hi all,

Through trial&error I've found out that the network must control the data rate when testing geolocalisation.

Best regards,
Bert
Reputatie 6
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Hi @Gabzz,

Below, the answer that I got from the specialists:

Yes, a situation may arise that the message is received on less than 3 gateways, or that reception signal differs so much that it is not relevant to the three-point measurement.
In that case, no update of the location will take place, but this will be reversed by the time-stamp DevLocTime (and the absence of an update).
Reputatie 6
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Hi Gabzz,

I agree with you that It is a bit difficult, but you understood it perfectly!
If I can help you with any other questions, please let me know 😉
Reputatie 6
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Hi @Corne van Strien,

Welkom bij de IoT Community!
Ik ben nogmaals mijn conversatie met de specialisten in gedoken en ik zie dat we nog niet tot een specifieke verklaring en oplossing gekomen zijn. Ik heb daarom direct het verzoek uitgezet om hier nogmaals in te duiken. Ik hoop hier z.s.m. een antwoord op te hebben.
Reputatie 6
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Hi @tonb,

Leuk om u weer terug te zien!
Goed dat u deze vragen stelt. Geolocation is voor zowel de Developer Portal als Thingpark gelijk. Echter is er op het gebied van nauwkeurigheid wel een klein verschil. We maken namelijk onderscheid tussen 4 categorieën devices namelijk static, slow moving, fast moving en nomadic. Per categorie hebben we een eigen nauwkeurigheid.

Op de Developer Portal is ervoor gekozen om een static profiel in te stellen. Dit is niet te wijzigen en zorgt er dus ook voor dat de nauwkeurigheid van een static profiel te verwachten is via de Developer Portal. Op dit moment is de nauwkeurigheid bij dit profiel 60 meter met een succes rate van 90%.

Nu is het natuurlijk zo dat we een landelijk dekkend netwerk hebben, maar natuurlijk zal de dekking en dus ook de nauwkeurigheid niet op elke plek gelijk zijn. Ik heb echter geen zicht op de sterke en de zwakkere plekken in het netwerk.
Hi @Tim,

Strange! I will look into it. Thanks for your time.

Jan
Reputatie 1
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@Gijs you need a LoRa subscription with the feature Geolocation activated. Then you need an application that sends some data (even if it is a dummy payload, so no specific changes needed in your application), then you need to make sure that at least 3 gateways can pick up your signal for triangulation, so you need to check your antenna effectivity, TX-power and SF, and then you will receive a new message type on your backend server, the DevEUI_location message that you need to decode. That's basically it 😉
Reputatie 1
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@Gijs You can forget better than GPS accuracy, the only thing you may achieve is better than GPS coverage. I think KPN strives for 20-50 meter accuracy, but they are not there yet. The actual accuracy depends on the geometry of the network, which is still changing from day to day because KPN still expands the number of sites, and it also depends on your location of course.
We have done a lot of tests and as a rough estimate I would say that in 80% of the cases, the accuracy lies between 20 and 200 meters.
Statistically, I would say the outdoor accuracy is better than indoor. Simply because the reception level indoor is less, this means fewer gateways receive your signal, and the triangulation quality is less.
I would like to test with geolocation. Is this possible? What do I need to do for that?
@Tim and @rharte
Thanks for the information. I can't wait to test with the geolocation funtionality. What can I expect from geolocation inside buildings? I am looking for an indoor solution that performs better than gps location.
@Tim A quick question:

Supposing my sensor is well within range of loc-enabled stations, could it be possible that I am not guaranteed to receive an update on each transmission because, for instance, the backend hasn't quality data to compensate for external factors (e.g issues of multi path or whatever the DTOA issue might occur).

My question boils down to understand if more than one transmission might still be required even in optimal network coverage of location-based gateways.
THX
@rharte Well put. That's an additional aspect I wanted to tackle.

I have the impression we can't possibly correlate location with a data transmission (that explains also why it's advertised for stationary objects).
For example, a JoinRequest might trigger a position update, yet no data payload is sent. The device might move, in the meanwhile, and end in a zone where multipath prevents location data to be computed effectively (i guess some kind of outlier filter is implemented). However the last known position would still be the one computed at JoinRequest time.

Am I completely off path?

One wonders if a LinkCheck might thus trigger a location update.
Reputatie 7
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Hi all,

Through trial&error I've found out that the network must control the data rate when testing geolocalisation.

Best regards,
Bert
Thanks for sharing your findings Bert! 🙂
Reputatie 7
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Hello Amine,

Do you have a contact at KPN for LoRa? Geolocation is as far as I know not yet accessible. If you're interested I can get you in touch to get access. Tests are only available in a limited number of locations and only valid for stationary cases.
Reputatie 7
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Will do Amine, please check your PM inbox 🙂
Reputatie 7
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Hello @jankappe, we are currently looking into this problem. I'll post an update if we make any progress.
Reputatie 7
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Hi @jankappe, can you share a JSON message with us? If possible, one normal, and one location type.
Reputatie 7
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Sorry for the delay @jankappe,

Thanks for sharing! I've forwarded your message to my colleagues. Hope we'll find the cause soon, I'll let you know. 🙂
Reputatie 7
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Hi @jankappe,

We cannot reproduce this! I have fetched the JSON message trough the developer portal, but if I send the message in uppercase letters, it will look like this again. The message is not changed on the way.
Therefore we think the problem should be found within your application server.
Reputatie 7
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No problem! Hope you find out what is causing this, please share your findings on the forum 🙂
Reputatie 7
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Hi Tim,

Could you help me get in touch with a KPN contact to get access and test Geolocation?

Many thanks

Gertjan

Sure! Can you sent me a PM with your DevEUI?

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