For attributes slope or ramp width, standard error of up to 5% is considered tolerable (in light of the large number of curbs to be surveyed and limited budget). For attributes such as whether a curb cut leads into a hazardous part of the intersection, inputs are qualitative and require human input. Location accuracy is important since each curb must be locatable for remedial works. 

3.2 Data collection methods

With these requirements under consideration, data collection was conducted through three methods: (i) smartphone-based survey; (ii) Structure Sensor; and (iii) LiDAR scanner.

(i) Smartphone-based survey

A survey tool was built using ESRI Survey123 software. The tool comprised 12 questions in a web-based survey form. Publicly available on the internet, the tool may be utilized by anyone with a smartphone, allowing multiple team members to gather data independently. Data is entered for each curb inspected by a team member, making use of smartphone GPS and measurements using a tape measure. A photo is taken of each curb cut. The survey tool may be viewed at http://bit.ly/2I85t5Z.
Construction of the survey questions required several iterations of field testing. Challenges included:
Having refined the survey tool, curb cuts were surveyed between 26th St and Union Square.