8848.86 — what comes to mind when you hear this number? That’s right, the height of Mount Everest. But why does this figure keep changing from what you remember? Recently, a surveying documentary titled 8848.86 held its preview screening in Lhasa and officially kicked off nationwide cinema promotion. We haven’t found any screening information in Wuhan yet, so we’ve gathered some material to give you a sneak peek.
What Cutting-Edge GIS Technologies Are Shown?
8848.86 isn’t just a number captured by casually taking a GPS reading at the summit — it’s the result of integrating and cross-checking multiple surveying technologies. The key techniques we know so far include:
- BeiDou GNSS Joint Observations: The summit and nine ground stations below conducted synchronous observations. By fusing BeiDou and GPS data, the geodetic height accuracy reached ±0.9 cm.
- Domestically Developed Snow Depth Radar: Operated in low-temperature environments, it detected the thickness of snow and ice on the summit to support the conversion to snow-surface height.
- Airborne Gravity + Summit Gravity Measurement: For the first time globally, airborne gravity was carried out on the north side of Everest, and the first-ever ground gravity measurement was made at the summit. The quasi-geoid accuracy improved to ±4.8 cm.
- Airborne LiDAR and Satellite Remote Sensing: Airborne laser scanning and the ZY-3 (Ziyuan-3) satellites captured 3D terrain and real-scene basemaps around Everest.
- Domestically Developed Long-Range Total Station: Used in parallel with traditional methods such as leveling and astronomical observation, multi-source data underwent layer-by-layer verification to lock in the final height.
A Surveying Documentary Without Special Effects
8848.86 takes the 2020 Everest height measurement as its main thread, weaving in the first ascent in 1960 and the remeasurements in 1975 and 2005. The film crew spent over 60 days filming above 5,000 meters, with no studio shoots and no special effects. It fully captures the two retreats forced by storms, the final summit push through heavy snow, and the 12 mountaineers who stayed on the summit for 150 minutes to complete BeiDou positioning, snow depth radar, and gravity measurements.
Zhang Zhonghui, deputy director of the First Geodetic Surveying Brigade, who participated in both the 2005 and 2020 measurements, revealed that the entire process — from preparation to the official release of the height — took two years. Team member Xu Weihang shared vivid details: trekking over treacherous slopes, eating instant noodles with melted snow and ice — these are the daily realities of surveying fieldwork.
Three Numbers and Sixty Years of Footage
The three officially released heights for Everest reflect the leaps in surveying capability: 8848.13 m in 1975 (the first measurement by Chinese surveyors), 8844.43 m in 2005 (rock height), and 8848.86 m in 2020 (snow-surface height, jointly announced by China and Nepal). From carrying instruments by manpower to using GPS, and then to an all-domestic kit — BeiDou, snow depth radar, and gravimeters — making measurements at the summit, each number represents the outcome of field station deployment, summit observations, indoor data processing, and rigorous multi-tier verification.
Another thread running through the film is the legacy of documentary imagery. The Central Newsreel and Documentary Film Studio has been filming Everest documentaries since the 1960s and 1970s. The new film uses 4K technology to seamlessly splice together black-and-white archival footage with the present-day field shots — somewhat akin to historical image registration and time-series analysis in surveying and remote sensing, using the camera to weave together the Everest memories of three generations of surveyors.
Summary
8848.86 is more than a string of numbers engraved in textbooks — it is a national elevation benchmark measured inch by inch by surveyors with their footsteps and instruments. The documentary 8848.86 brings this entire technical chain to the big screen in 85 minutes. Starting in July, it will be screened nationwide. If it comes to your city, why not go and see it?