野外基线是测绘科学技术领域中特殊的长度实物标准，可用来检定全站仪等光电测距仪的加、乘常数，为确保检定结果的真实、准确、可靠，定期进行野外基线的溯源是必不可少的。目前我国主要采用24 m因瓦尺或高精度光电测距仪2种方法实现野外基线的溯源，已有大量实验事实表明，我国野外基线的量值传递与国外仍存在着不一致的问题。随着我国制造业的快速发展和“中国制造2025”的提出，传统的野外基线溯源技术很难满足越来越高的精度要求，迫切地需要实现野外基线精密测距。结合国内外研究现状，对光干涉法、24 m因瓦尺法和高精度光电测距法进行总结，深入分析了3种野外基线溯源方式的优缺点。最后，对我国未来的基线场建设提出了一些思考与建议。
Outdoor baseline is the special length standard in the field of surveying and mapping, it can be used to verify the addition and multiplication constants of the total station and other photoelectric rangefinders. In order to ensure the authenticity, accuracy and reliability of verification results, conducting outdoor baseline traceability periodically is essential. At present, direct measurement by 24 m invar tape or high precision electro-optical measurement is mainly used to achieve the traceability of outdoor baseline in China, a large number of experimental facts have shown that there are still system errors between the quantity transfer of baselines in China and abroad. With the rapid development of China′s manufacturing industry and the proposal of “made in China 2025”, the traditional traceability technology of outdoor baseline is difficult to meet the increasingly high precision requirements, and it is urgent to achieve the outdoor baseline precision ranging. Combined with the current research situation at home and abroad, optical interferometry by Vaisala interference comparator, direct measurement by 24 m invar tape and high precision electro-optical measurement are summarized，the advantages and disadvantages of the three methods are deeply analyzed. Last but not least, some thoughts and suggestions are put forward for the future outdoor baseline field construction in China.