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Frequently Asked Questions (FAQ)
These questions and answers will be updated as new information becomes available over time. The questions are focused on creating partnerships for acquisition, but as the process moves along, will address data access, use and training.
Lidar Data Quality Levels
What is QL?
QL stands for Quality Level. QL determines the quality of lidar data, based on US. Geological Survey (USGS) definitions. Handout - Why 3DGeo Supports QL1
What is the difference between QL0, QL1, QL2 and QL3?
USGS has defined various value levels of lidar data based on factors in the following table.
| LBS | Aggregate nominal pulse spacing and density |
Absolute vertical accuracy |
Minimum digital elevation model cell size |
Supported Contour Interval |
||||
|---|---|---|---|---|---|---|---|---|
| Quality Level |
Aggregate nominal pulse spacing (m) |
Aggregate nominal pulse density (pls/m2) | RMSEz (nonvegetated) (m) | NVA at the 95% confidence level (m) | VVA at the 95 percentile (m) | Minimum cell size (m) | Minimum cell size (ft) | In Feet |
| QL0 | ?0.35 | ?8.0 | ?0.050 | ?0.098 | ?0.15 | 0.5 | 1 | 0.5 |
| QL1 | ?0.35 | ?8.0 | ?0.100 | ?0.196 | ?0.30 | 0.5 | 1 | 1.0 |
| QL2 | ?0.71 | ?2.0 | ?0.100 | ?0.196 | ?0.30 | 1 | 2 | 1.0 |
| QL3 | ?1.41 | ?0.5 | ?0.200 | ?0.392 | ?0.60 | 2 | 5 | 2.0 |
LBS - Lidar Base Specification (USGS 2020 rev. A) RMSEz - root mean square error in the z direction; NVA - nonvegetated vertical accuracy; VVA - vegetated vertical accuracy
Why QL1?
To meet and exceed the USGS's minimum high-quality data standards to ensure the broadest base of end-user applications and higher return on investment for all. QL1 enables the creation of several high quality derived datasets, including:
- DEMS at 50 centimeter (half-meter) resolution
- 1-foot contours
- Detailed above ground feature mapping (e.g., building footprints and vegetation structure), and
- Resolved water conveyance features (e.g., sewers, culverts, and other human made infrastructure).
Lidar Data Acquisition Deliverables and Costs
What data and products will we get if we contribute to 3DEP?
- Point Cloud (classified to minimum level - meets most needs; data hosted online)
- Digital Elevation Model (DEM/Bare-Earth Surface Raster)
- Lidar Swath Polygon
- Hydro-breaklines
- Metadata
- Collection report
- Survey report - of all ground survey data
- Flight Mission Report
- Processing Report - Calibration & Classification
- QA/QC Report - accuracy assessment
- Georeferenced polygon swaths
- Georeferenced polygon extents
What are Possible Added Deliverables?
Possible Added Deliverables are not 3DEP funded deliverables, but can be part of the 3DEP contract as additional products and services with the 3DEP contract vendor.
- Higher density Point Cloud (3DGeo advocates for QL1, partners may upgrade areas to QL0)
- Improved hydrographic products
- Advanced hydro-modified DEM (Conditioned)
- Bare Earth point cloud
- Additional Point Classification
- High vegetation and buildings
- Intensity imagery, GeoTIFF
What are Foundational Derived Products?
Foundational Derived Products are publicly available data served as authoritative products from state agency distribution portals.
- 1-ft Contour Dataset
- Hillshaded DEM
- Canopy Height Model (CHM)
- Other products to come?
What will this cost my organization?
The cost will vary by LAA based on how many partnerships can be found and the number of counties that participate. The larger the contiguous area, the cheaper it will be. The more partners, the cheaper it will be for each partner. Initially, we will provide a cost range based on other current projects. As Minnesota's lidar acquisition moves along, the USGS will provide an updated the 3D Geomatics Committee with a per mile cost that we will share.
Whose plan is this?
This is not a plan BY the State of Minnesota, it is a plan FOR the state of Minnesota. This plan was developed by a Committee with several members across all levels of government and the private sector IN Minnesota FOR Minnesota. Feedback on the Plan content and additions/contributions to the Case Studies included in the Plan are welcomed by all.
The architecture of 3DGeo (PDF) brings dozens of stakeholders together to serve common goals under one Geospatial Advisory Council charter. 3DGeo is comprised of subject matter experts organized by workgroup sectors. Each workgroup operates by the guidance of its own work plan. Workgroup members specialize in data development, management, dissemination, application, and end user business needs.
What is the goal of this plan?
Collect high density lidar at QL1 in every part of the state over the course of several years, in tandem with the USGS 3DEP plan.
About GAC and the 3D Geomatics Committee
What is the Minnesota Geospatial Council?
The Minnesota Geospatial Council (GAC) acts as a coordinating body for the Minnesota geospatial community. It represents a cross-section of organizations that include counties, cities, universities, business, nonprofit organizations, federal and state agencies, tribal government, and other stakeholder groups that benefit from geospatial technology.
What is the 3D Geomatics Committee?
The 3D Geomatics Committee (3DGeo) is a committee chartered under the Minnesota Geospatial Advisory Council (GAC). The 3D Geomatics Committee is committed to identifying and promoting the need for planning, training, funding, acquisition, and management of three-dimensional geomatic data and derived products for Minnesota.
Who are 3DGeo Committee Members?
Find a list of the committee members.
The committee created a plan for the state of Minnesota, to work with state, county, tribal, and city governments. Committee members have expertise in lidar data standards, communication with vendors and Minnesota's Master Contract, big data management and dissemination, the USGS 3DEP Plan, GIS/Lidar education, building stakeholder involvement, and development of foundational and authoritative datasets.
Common Terms
What is an LAA?
An LAA is a Lidar Acquisition Area (LAA). The 3DGeo Committee developed LAAs to serve as collaboration regions to meet a diversity of stakeholder needs. Lidar data is often used to understand natural phenomenon but is coordinated and funded by local governments. The lidar plan attempted to strike a balance between natural and geopolitical boundaries by merging the boundaries of major river basins with the political boundaries of counties into lidar acquisition areas (LAA) across Minnesota.
Why is the state divided into Lidar Acquisition Areas (LAA)?
The state is divided into LAAs to allow for regional stakeholder engagement and funding coordination while leveraging federal contributions, and additional cost share opportunities. The LAAs attempt to strike a balance between natural and geopolitical boundaries by merging the boundaries of major river basins with the political boundaries of counties. Additionally, an area larger than an LAA, or a statewide lidar collection within the same time window is not feasible, and so sub-areas of the state were needed.
What is an LAB?
An LAB is a Lidar Acquisition Block (LAB). Some Lidar Acquisition Areas (LAA) are broken into smaller Lidar Acquisition Blocks (LAB). This was done in LAAs that were large and were the potential for funding and/or data collection at one time was anticipated to be a challenge, or if the LAAs were naturally broken into sub-watershed areas.
Federal Coordination
What is 3DEP?
The 3D Elevation Program (3DEP) is a USGS National Geospatial Program that systematically guides the collection of 3D elevation data in the form of light detection and ranging (lidar) data for the United States, and the U.S. territories. To be considered for partnership 3DEP funds, partner entities need to submit a proposal responding to a Broad Agency Announcement (BAA).
What is BAA?
Broad Agency Announcement (BAA) is the grant coordinating mechanism for the 3D Elevation Program (3DEP). It guides partnerships between the US Geological Survey (USGS) and other Federal agencies with other public and private entities seeking high-quality 3D lidar elevation data acquisition.
Federal agencies, state and local governments, tribes, academic institutions and the private sector are eligible to submit proposals through the BAA process.
Applicants may contribute funds toward 3DEP lidar data acquisition activity managed by the USGS (Geospatial Products and Services Contracts, GPSC) or they may request 3DEP funds toward a lidar data acquisition activity where the requesting partner is the acquiring authority (Cooperative Agreement).
What is SeaSketch?
SeaSketch is an online spatial mapping platform that the 3DGeo Committee is using to coordinate Minnesota's Lidar Plan. It allows Minnesota to eliminate redundant efforts, coordinate funding, schedules, priorities, specifications, and sensors to ensure the acquisition of lidar data serves the greatest amount of needs. We created a handout to assist you in adding your area of interest to SeaSketch. You can also just look to see what agencies are interested in collaborating in your area.
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