Add need for the package and links to READE and intro vignette

README.Rmd

@@ -26,6 +26,10 @@ The **slopes** R package calculates the slope (longitudinal steepness, also know
 - [vector](https://geocompr.robinlovelace.net/spatial-class.html#vector-data) linestring geometries defined by classes in the [`sf`](https://r-spatial.github.io/sf/) package
 - [raster](https://geocompr.robinlovelace.net/spatial-class.html#raster-data) objects with pixel values reporting average height, commonly known as digital elevation model (**DEM**) datasets, defined by classes in the [`raster`](https://cran.r-project.org/package=raster) or more recent [`terra`](https://rspatial.org/terra) packages
 
+Data on slopes are useful in many fields of research, including [hydrology](https://en.wikipedia.org/wiki/Stream_gradient), natural hazards (including [flooding](https://www.humanitarianresponse.info/fr/operations/afghanistan/infographic/afg-river-gradient-and-flood-hazard) and [landslide risk management](https://assets.publishing.service.gov.uk/media/57a08d0740f0b652dd0016f4/R7815-ADD017_col.pdf)), recreational and competitive sports such as [cycling](http://theclimbingcyclist.com/gradients-and-cycling-an-introduction/), [hiking](https://trailism.com/trail-grades/), and [skiing](https://www.snowplaza.co.uk/blog/16682-skiing-steeps-what-does-gradient-mean-ski-piste/).
+Slopes are also also important in some branches of [transport and emissions modelling](https://www.sciencedirect.com/science/article/pii/S2352146516302642) and [ecology](https://doi.org/10.1016/j.ncon.2016.10.001).
+See the [`intro-to-slopes` vignette](https://itsleeds.github.io/slopes/articles/intro-to-slopes.html) for details on fields using slope data and the need for this package.
+
 This README covers installation and basic usage. For more information about slopes and how to use the package to calculate them, see the [get started](https://itsleeds.github.io/slopes/) and the [introducion to slopes](https://itsleeds.github.io/intro-to-slopes/) vignette.
 
 

README.md

@@ -25,6 +25,24 @@ features, based on two main inputs:
     the [`raster`](https://cran.r-project.org/package=raster) or more
     recent [`terra`](https://rspatial.org/terra) packages
 
+Data on slopes are useful in many fields of research, including
+[hydrology](https://en.wikipedia.org/wiki/Stream_gradient), natural
+hazards (including
+[flooding](https://www.humanitarianresponse.info/fr/operations/afghanistan/infographic/afg-river-gradient-and-flood-hazard)
+and [landslide risk
+management](https://assets.publishing.service.gov.uk/media/57a08d0740f0b652dd0016f4/R7815-ADD017_col.pdf)),
+recreational and competitive sports such as
+[cycling](http://theclimbingcyclist.com/gradients-and-cycling-an-introduction/),
+[hiking](https://trailism.com/trail-grades/), and
+[skiing](https://www.snowplaza.co.uk/blog/16682-skiing-steeps-what-does-gradient-mean-ski-piste/).
+Slopes are also also important in some branches of [transport and
+emissions
+modelling](https://www.sciencedirect.com/science/article/pii/S2352146516302642)
+and [ecology](https://doi.org/10.1016/j.ncon.2016.10.001). See the
+[`intro-to-slopes`
+vignette](https://itsleeds.github.io/slopes/articles/intro-to-slopes.html)
+for details on fields using slope data and the need for this package.
+
 This README covers installation and basic usage. For more information
 about slopes and how to use the package to calculate them, see the [get
 started](https://itsleeds.github.io/slopes/) and the [introducion to

vignettes/intro-to-slopes.Rmd

@@ -23,17 +23,20 @@ library(slopes)
 
 Although there are several ways to name "slope", such as "steepness", "hilliness", "inclination", "aspect", "gradient", "declivity", the referred `slopes` in this package can be defined as the "longitudinal gradient" of linear geographic entities, as defined in the context of rivers by[@cohen_global_2018].  
 
-The package was initially developed to research road slopes but has also been used to calculate and visualise slopes of rivers and trajectories representing movement on roads, using an open dataset published by [@ariza-lopez_dataset_2019].
+The package was initially developed to research road slopes to support evidence-based sustainable transport policies.
+Accounting for gradient when planning for new cycling infrastructure and road space reallocation for walking and cycling can improve outcomes, for example by helping to identify routes that avoid steep hills.
+The package can be used to calculate and visualise slopes of rivers and trajectories representing movement on roads of the type published as open data by @ariza-lopez_dataset_2019.
 
-\
+Data on slopes are useful in many fields of research, including [hydrology](https://en.wikipedia.org/wiki/Stream_gradient), natural hazards (including [flooding](https://www.humanitarianresponse.info/fr/operations/afghanistan/infographic/afg-river-gradient-and-flood-hazard) and [landslide risk management](https://assets.publishing.service.gov.uk/media/57a08d0740f0b652dd0016f4/R7815-ADD017_col.pdf)), recreational and competitive sports such as [cycling](http://theclimbingcyclist.com/gradients-and-cycling-an-introduction/), [hiking](https://trailism.com/trail-grades/), and [skiing](https://www.snowplaza.co.uk/blog/16682-skiing-steeps-what-does-gradient-mean-ski-piste/).
+Slopes are also also important in some branches of [transport and emissions modelling](https://www.sciencedirect.com/science/article/pii/S2352146516302642) and [ecology](https://doi.org/10.1016/j.ncon.2016.10.001).
+A growing number of people working with geospatial data require accurate estimates of gradient, including:
 
-A growing number of people working with geospatial data and require accurate estimates of gradient.
-
-- Transport planning practitioners require accurate estimates of roadway gradient for estimating energy consumption, safety and mode shift potential in hilly cities (such as Lisbon, the case study city used in the examples in the documentation). 
-- Vehicle routing models that are sensitive to going up or down steep hills (e.g. bicycles, trains, and large trucks), such as active travel planning, logistics, and emergency services.
+- Transport planning practitioners who require accurate estimates of roadway gradient for estimating energy consumption, safety and mode shift potential in hilly cities (such as Lisbon, the case study city used in the examples in the documentation). 
+- Vehicle routing software developers, who need to build systems are sensitive to going up or down steep hills (e.g. bicycles, trains, and large trucks), such as active travel planning, logistics, and emergency services.
 - Natural hazard researchers and risk assessors require estimates of linear gradient to inform safety and mitigation plans associated with project on hilly terrain.
-- We believe that aquatic ecologists, flooding researchers and others could benefit from estimates of river gradient to support modelling of storm hydrographs, although we do not have experience in these domains
-- Other domains, such as: agriculture, geology, and infrastructure constructions. 
+- Aquatic ecologists, flooding researchers and others, who could benefit from estimates of river gradient to support modelling of storm hydrographs
+
+There likely other domains where slopes could be useful, such as agriculture, geology, and civil engineering.
 
 An example of the demand for data provided by the package is a map showing gradients across Sao Paulo (Brazil, see image below) that has received more than 300 'likes' on Twitter and generated conversations:  https://twitter.com/DanielGuth/status/1347270685161304069