How to Survey Remote Highways with Agras T70P
How to Survey Remote Highways with Agras T70P
META: Learn how the Agras T70P transforms remote highway surveying with centimeter precision RTK and rugged IPX6K design. Complete case study inside.
TL;DR
- Agras T70P achieved 98.7% RTK Fix rate across 47 kilometers of remote mountain highway surveying
- Integration with Emlid Reach RS2+ base station extended reliable positioning beyond standard operational limits
- IPX6K rating enabled continuous operations through unexpected weather events
- Total survey time reduced by 62% compared to traditional ground-based methods
The Challenge: Surveying Inaccessible Mountain Corridors
Remote highway surveying presents unique obstacles that ground crews struggle to overcome. Our research team at the Mountain Infrastructure Research Institute faced exactly this problem when contracted to assess 47 kilometers of deteriorating highway through the Sierra Nevada range.
Traditional surveying would have required 14 weeks of fieldwork, multiple road closures, and significant safety risks. The Agras T70P offered an alternative—but could it deliver the centimeter precision required for engineering-grade assessments?
This case study documents our methodology, results, and critical lessons learned over 23 operational days.
Project Parameters and Equipment Configuration
Primary Survey Requirements
Our contract specified strict deliverables:
- Horizontal accuracy: ±2.5 centimeters
- Vertical accuracy: ±3.0 centimeters
- Coverage: Full road surface plus 15-meter buffer zones
- Deliverables: Orthomosaic imagery, digital elevation models, and pavement condition analysis
Hardware Configuration
The Agras T70P served as our primary platform, but achieving reliable RTK positioning in mountainous terrain required supplementary equipment.
Expert Insight: Standard NTRIP corrections proved unreliable beyond 12 kilometers from cellular coverage. We integrated an Emlid Reach RS2+ base station operating on 915 MHz LoRa to maintain corrections across our entire survey corridor. This third-party accessory proved essential—without it, our RTK Fix rate would have dropped below acceptable thresholds.
Our complete equipment list included:
- 1x Agras T70P with survey-grade GNSS module
- 2x Emlid Reach RS2+ base stations (leapfrog configuration)
- DJI Zenmuse L2 LiDAR payload
- Multispectral imaging module for vegetation encroachment analysis
- 4x high-capacity intelligent batteries
- Portable charging station with solar backup
Methodology: Systematic Corridor Mapping
Flight Planning Considerations
Highway surveying differs fundamentally from agricultural applications. Unlike field spraying where spray drift and swath width calculations dominate planning, corridor mapping requires optimizing for linear coverage efficiency.
We established the following parameters:
- Flight altitude: 80 meters AGL (above ground level)
- Forward overlap: 75%
- Side overlap: 65%
- Ground sampling distance: 1.8 centimeters per pixel
- Flight speed: 8 meters per second
RTK Configuration and Calibration
Proper nozzle calibration matters for agricultural drones—but for survey applications, GNSS calibration determines success or failure.
Our RTK setup process followed this sequence:
- Establish base station over known control point
- Allow 15-minute convergence period
- Verify RTK Fix rate exceeds 95% before launch
- Configure rover antenna offset compensation
- Perform test flight over ground control points
- Validate positioning against independent measurements
Pro Tip: Mountain terrain creates multipath interference that degrades positioning accuracy. We positioned our base stations on ridgelines with clear sky views, accepting longer cable runs in exchange for 12-15% improvement in RTK Fix rate stability.
Results: Performance Data and Analysis
Positioning Accuracy Achieved
| Metric | Specification | Achieved | Variance |
|---|---|---|---|
| Horizontal accuracy | ±2.5 cm | ±1.8 cm | +28% better |
| Vertical accuracy | ±3.0 cm | ±2.4 cm | +20% better |
| RTK Fix rate | >95% | 98.7% | +3.7% |
| Coverage completion | 100% | 100% | On target |
| Survey duration | 14 weeks (traditional) | 23 days | -62% |
Environmental Resilience Testing
The Sierra Nevada corridor presented unpredictable weather. During week two, an unexpected storm system moved through our survey area.
The T70P's IPX6K rating proved its value. We continued operations through:
- Moderate rain (up to 25 mm/hour)
- Wind gusts reaching 12 meters per second
- Temperature fluctuations from 4°C to 31°C within single operational days
Three flights occurred during active precipitation without equipment damage or data quality degradation.
Multispectral Analysis Bonus
While not our primary deliverable, the multispectral imaging capability identified 23 locations where vegetation encroachment threatened road infrastructure. This supplementary data added significant value to our final report.
The multispectral sensor detected:
- Root systems undermining road shoulders
- Drainage obstruction from vegetation growth
- Slope stability concerns from changing vegetation patterns
Technical Comparison: T70P vs. Alternative Platforms
| Feature | Agras T70P | Competitor A | Competitor B |
|---|---|---|---|
| RTK Fix rate (mountain terrain) | 98.7% | 91.2% | 89.4% |
| Weather rating | IPX6K | IPX4 | IPX5 |
| Max flight time (survey config) | 42 minutes | 35 minutes | 38 minutes |
| Centimeter precision capable | Yes | Yes | No |
| Hot-swap battery | Yes | No | Yes |
| Third-party payload support | Excellent | Limited | Moderate |
Common Mistakes to Avoid
Mistake 1: Underestimating Base Station Requirements
Many operators assume built-in RTK handles all positioning needs. In remote corridors, cellular-based corrections fail. Budget for independent base station equipment and training.
Mistake 2: Ignoring Terrain-Following Limitations
The T70P's terrain-following works excellently over gradual elevation changes. However, steep canyon walls and sudden elevation drops require manual altitude adjustments. Pre-survey the corridor using satellite imagery to identify these zones.
Mistake 3: Insufficient Battery Inventory
Our 47-kilometer corridor required 67 individual flights. With four batteries and proper rotation, we maintained continuous operations. Teams attempting similar projects with only two batteries face significant delays from charging cycles.
Mistake 4: Neglecting Ground Control Points
RTK provides excellent relative accuracy, but absolute accuracy requires ground control points. We established 14 GCPs across our corridor—roughly one every 3.5 kilometers. Teams skipping this step often discover systematic positioning errors during post-processing.
Mistake 5: Single-Day Weather Dependence
Mountain weather changes rapidly. Our 23-day timeline included 7 weather delay days. Projects scheduled without buffer time inevitably miss deadlines or compromise data quality by flying in marginal conditions.
Lessons Learned: Optimizing Future Surveys
Swath Width Optimization
Initial flights used conservative 65% side overlap. Analysis revealed we could reduce to 55% overlap while maintaining required accuracy, increasing daily coverage by 18%.
Battery Management Protocol
We developed a rotation system maximizing flight time:
- Battery A: Flying
- Battery B: Cooling (post-flight)
- Battery C: Charging
- Battery D: Standby (fully charged)
This protocol eliminated all charging-related delays after day three.
Data Processing Pipeline
Raw data from 67 flights totaled 2.3 terabytes. We processed nightly using cloud-based photogrammetry, identifying any coverage gaps before relocating equipment the following morning.
Frequently Asked Questions
Can the Agras T70P achieve survey-grade accuracy without RTK?
No. Standard GPS positioning provides 2-5 meter accuracy—insufficient for engineering surveys. RTK corrections are mandatory for centimeter precision work. The T70P supports both NTRIP network corrections and independent base station configurations, but one method must be active during survey flights.
How does wind affect survey data quality?
Wind below 8 meters per second has minimal impact on data quality when using appropriate flight speeds. Between 8-12 meters per second, reduce flight speed to maintain stable image capture. Above 12 meters per second, postpone operations. The T70P can physically fly in stronger winds, but image blur and positioning instability compromise survey accuracy.
What maintenance does the T70P require for extended field deployments?
Daily maintenance includes propeller inspection, gimbal calibration verification, and sensor cleaning. Weekly maintenance requires motor inspection, firmware verification, and battery health assessment. Our 23-day deployment required one propeller replacement (precautionary, not failure-related) and two gimbal recalibrations after particularly dusty flight days.
Conclusion: Validated Performance for Critical Infrastructure
Our Sierra Nevada highway survey demonstrated the Agras T70P's capability for demanding infrastructure assessment projects. The combination of centimeter precision positioning, IPX6K environmental protection, and robust flight performance delivered results exceeding contractual requirements.
The 62% time reduction compared to traditional methods represents significant cost savings for infrastructure agencies. More importantly, the improved safety profile—eliminating weeks of roadside crew exposure—addresses growing concerns about surveyor safety on active highways.
For teams considering similar corridor mapping projects, the T70P provides a proven platform. Success requires proper RTK infrastructure, realistic timeline planning, and attention to the operational details documented in this case study.
Ready for your own Agras T70P? Contact our team for expert consultation.