Low-Cost GPS Tracking System

[ciolt]

Not entirely related to transit docs, but cities like Sweetwater have piloted a small real-time tracking system before. It eventually died off since the developer disappeared(?) and the expenses of $5/month were too high. Ideally, cities are interested in low-cost but effective solutions that will improve ridership. Real-time tracking and accessible data is one way to do that.

Here I'll be listing some ways to cut down costs on wireless-based GPS trolley tracking.

[ciolt]

Cellular Data Approach

An estimate for data usage is around 8-10MB/mo per vehicle. Prices on this one are iffy, but some providers have IoT services that offer pay-as-you-go schemes. The only issue is that these can become overpriced really fast.

• T-Mobile IoT: $0.60/mo + $0.025/MB (1st included) = $0.83/mo
• USMobile: $2/mo for 100MB
• Soracom: $1.8/mo (active service fee) + $0.73/mo (10MB usage) = $2.53/mo
• SpeedTalk Mobile: $5/month for 100MB, 100 texts (fallback?), and 50min voice
• Aeris: $5/month for 10MB + overage fees
• Hologram: $1.50/mo + $0.40/MB = $5.50/mo

Text-based Approach

A median estimate for 15-second interval updates over 30 days is about 90K texts. Assuming a 90-byte packet size (out of 160 max) for the trolley number, direction, lat/long, and onboard system time (to calculate delay from sent/received at the server). An SMS-based protocol will have to be used to relay data if it's more cost-efficient than using data-only cellular services.

Sending data

• Tello: $5/month for unlimited texts
• Xfinity Mobile: Free, but only to Xfinity Internet subscribers (may be limited)

Receiving data

• Plivo: Free
• Twilio: $0.0075/text