# Landscape Units A Landscape Unit (LSU) is a collection of HRUs. It can be equivalent to a subbasin, a floodplain or upland unit, or a grid cell with multiple HRUs. LSUs are currently only used for summarizing landscape outputs. Two files are needed to define which HRUs are part of which LSU: * [ls\_unit.def](/io-docs/introduction-1/landscape-units/ls_unit.def.md) specifies which HRUs a LSU contains. * [ls\_unit.ele](/io-docs/introduction-1/landscape-units/ls_unit.ele.md) lists all HRUs and their corresponding LSU and basin fractions. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://swatplus.gitbook.io/io-docs/introduction-1/landscape-units.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.